Sorry for the off topic post, but...
There is a mod to cut the 5v rail on the Sanguinolou.
From http://reprap.org/wiki/Sanguinololu
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Bugs:
The USB 5V VBUS is connected to the output of the 5V regulator. This is bad for the regulator and bad for the PC. Some users report the regulator getting very hot (because it is trying to power the PC), other users report the PC giving USB over current errors. Nophead and Nothinman recommend cutting the 5V track to the USB connector. The only downside is the board needs the 12V supply before it will do anything, but who cares?
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I found that my PC was very occasionally shutting itself down as it saw a power spike on the 5v rail which always happened mid print no matter how long my PC was on. Since cutting the track I have no problems at all. Plus there is now less current draw of the USB bus.