A lot of people seem to be very reluctant to use their laptop ungrounded (by use of 2-to-3 prong adapter or removal of ground pin on power supply - basically disconnecting, removing or "lifting" a connection to ground somewhere in your system). The reasoning behind this reluctance to do this seems to be that you are exposing yourself to power surges and damaging your equipment. Although there is some degree of truth to this, it has really been elevated almost to the point of urban myth... Yes it is possible to fry your electronic equipment if it is not properly grounded, BUT it is very, very unlikely. Those people who tell you not to ever do this are usually in my experience either: paranoid alarmists, IT & computer engineers or studio audio/video guys. I'm not going to say that they are wrong... just that they are a bit overzealous. Having worked in some related fields, I know that what I was taught in the lab, server room or studio and what I experience in real world out in the field are very, very different. Honestly, in our business (as DJs) you have much higher chances of a drink getting spilled or even thrown on your laptop than having it taken out by a power surge. Even if you have a "no drinks" policy in your DJ booth, you know what kind of crap happens at a good party... LOL. As a professional live-sound engineer by day, I can tell you that in my industry, an AC ground lift is a standard piece of equipment in my tech-kit. We don't use it a lot because most of the time we have professional electricians dropping power for us to suit our exact needs, but when you are at a different venue every day there is always some place with crappy power or ground, etc. Only once in my 8 years as an audio technician for large concerts, conventions and other events, have I seen equipment get burned out due to a power problem... that was because the electrician wired it wrong (2 hot lines instead of 1 hot and 1 neutral). Every other time that there was some type of power issue, the equipment may have acted up, but the only piece of equipment that was blown (if at all) was the surge protector - after the power issue was fixed and equipment restarted, everything worked fine. YES, it is true - ideally speaking you should have proper power and ground. But as a DJ, it is not my responsibility to troubleshoot power and ground in some nightclub that is only paying me only so much for just a few hours work. If I was setting up my own nightclub or studio that would be different, but if you are doing live stuff in who knows how many different venues every day of the week, you just gotta be prepared to deal with it and that little adapter can save your life. Why this is reasonably safe: Most decent laptop power supplies will automatically adjust for fluctuations in frequency and voltage (most desktop computer power supplies do this as well). In the US, 120volts 60 Hz is the standard for AC power, but my Dell laptop power supply will handle roughly from 50-60Hz and 100-240volts. This means for most AC power surges or brownouts you will still be covered provided you use a good-quality surge protector (or as someone else suggested a UPS). This is why many laptops (even high-end ones such as Sony or Apple) don't even come with a 3-prong power cord - it isn't really very necessary. In my opinion, the only reason that certain laptopos, most notably Dell, Compaq/HP and Thinkpads, have a 3-prong power supply in the first place is because they are going after the corporate market and some large corporations or government agancies have restrictive guidelines for what kind of electrical equipment they can buy (for liability purposes they can only get grounded electrical equipment). The laptop power supply should cover for most AC power problems - what about direct current(DC) spikes coming over the AC lines? A good surge protector should cover for large DC voltage spikes and surges. If something does happen, it may blow the surge protector/UPS or even the laptop power supply, but chances are your laptop will be OK. Chances are that if your laptop gets fried, it was something truly unforseen like a lightning strike on your building or right outside the building and even if you had your equipment grounded it still would have ended up being fried. In terms of the kinds of noise and hum I have seen when using Traktor and Final Scratch, there are TWO potential sources of noise and hum that can get into your system via a grounded laptop power supply. The first is a pretty standard audio hum that is caused by one of the other componenets in the audio signal chain and a mismatched ground - it could be mixers, amps, or even lighting and lighting controllers hooked up on the same circuit. Anyone who has played on turntables knows the sound of a turntable ground wire that is loose or disconnected. There are other variations of audio hum and noise, but they are usually characterized buy a constant background noise that is limted to a pretty narrow pitch or frequency range. Yes it is true, this kind of noise can often be fixed by placing a ground hum eliminator or isolator ("Iso") at the correct place in the audio signalchain. (Not always - I've had times where I had to use an ISO, but also had to lift the ground on the power for a certain piece of equipment). I carry both with me because sound and audio are a part of both my day and night jobs. However when dealing with laptops, that is not the only type of noise... The second type of noise is something I saw for the first time with my laptop when i used Final Scratfch 1.5. It is a noise caused by computer equipment (especially hard drives and CD drives) that gets into the output from your sound card (internal laptop and/or external usb/firewire, etc.). The sound of this type of noise is different than the usuall audio humm or rizz. It is a digital sounding noise that is not a constant tone and may get louder or softer as your computer sends data to/from drives our soundcards. Some laptops, drives and soundcards are more prone to this noise than others, but usually it is most noticeable when using an external device over Firewire, USB, etc. The only fix that I know of for this digital type of noise involves disconnecting or "lifting" a grounding cable or connection somewhere in your system. My quickest fix is lifting the ground on the laptop power supply - that should kill it. The other possible fix is to cover the outer metal jacket of any usb firewire connectors with a small piece of electrical tape. I prefer the ground lift because I don't want to risk damaging the USB or firewire jacks and plugs with tape residue or by jamming a larger tape-covered plug into the jack. The only other fix for this would be very expensive and time consuming - buying different soundcards, computers and hard drives until you find a combination with little or no noise. To summarize... This is my advice if you are really worried about lifting the ground from your laptop power supply because you are afraid of frying your system from a power spike or other power-problems: (a lot of this is common sense, but I'm including it anyways) First - invest in a good surge protector, power conditioner and/or UPS. I have a $50 surge protector from Monster Cable that even has an audible alarm on it. It came with a lifetime warranty and I already had it replaced once because of an incorrectly wired socket - the alarm went off as soon as I plugged it in and before I had even turned on the master switch to power my sound system on. It did it's job and saved my system. Second - you should learn to differentiate between audio hum/noise and digital noise. For audio hum/noise, get an ISO or Hum Eliminator. For digital noise use a ground lift or put tape on the connectors of the problem USB or Firewire device. Third - if you are still worried, start saving up for a backup computer and other backup equipment. For example, because both my day and night jobs depend on computers, I have 1 computer for DJing and another one for my audio work, but I have duplicate software on both so I can also use each one as a backup in case the other dies. I also keep my "Traktor" folder on my external hard drive with my music collection so that whichever computer I am using I will always have all my playlists, etc. ready for me to use. The external hard drive I take on gigs is not my only copy - I have another bigger hard drive i keep at home with all my music and other vital files on it. This way if one of the drives gets corrupted, you have another copy of everything. Fourth - if you intend on really getting serious about DJing, music production or related fields as a career or sideline, learn your craft. Read some books or take some classes or seminars on audio basics, electricity/wiring, computers, etc.