Help!! Computer turns off while running Itunes

[brentg33]

hi, I have a Toshiba notebook running XP pro w/ a 60gb HD and a external 250GB running via usb 2.0. I have my itunes music folder stored on the external drive (G:) and have been running this way successfully since last August. Recently, (within the last 2 weeks or so) I was adding a new folder of music (artist discography) and some of the files needed itunes to convert from WMA. It seems while doing this conversion, the computer turns off....i tried this several times, with the same results until finally it led to the computer not being able to boot up (blue screen of death after XP loading screen) I re-imaged my computer from an old ghost image i had from when the computer was working correctly...but i still have the same issue...sometimes Itunes wont even start, and if it does start....eventually the computer will turn off.....i ran virius checks via mcafee....and that has come back clean...i did get rid of the artist discography which i though started the problem, but the problem is still there.....interestingly enough, i tried running a registry cleaning program and while that has run fine in the past...the registry program quits in the middle of scanning the registry now.....so i dont know if the issue is with the computer, the internal HD, itunes, or the external HD (G:)...please help!!!!!!
thanks
brent