Lost Hard Drive Space And A Blue Screen

1.I have a dell digital jukebox mp3 player that allows for storage of data or music. I tried to copy a 600mb file from the mp3 player onto my hard drive. I had a little over 600 mb of space left on my hard drive (a total storage capacity of 6GB). It said i had run out of space. So i deleted some files, move some things around and i had 1.1 GB of space free for this transfer. i tried again and this time again the message i got was not enough space on drive c:/. So i cancelled out and checked to see what i had on my hard drive, 500mb free!!!?? So i have lost hard drive space and not gain a file...So i investigated and found that i have 1.81 GB of data on c: documents settingsuser. but once i get into user, i have 6 folders none of which display nearly that much data. They are, favorites, start menu, cookies, desktop, my documents, and a file named ntuser. the ntuser file is 1mb, and my desktop has 700 or so mb on it. So my question is how can i get back this lost hd space,

2.Blue screen. Im on xp pro sp1, i use adaware, registry mechanic, and im generally tidy with my windows; note, reinstalling windows did not solve this. I never used to have this issue, but lately when i go to open or close certain programs i jump to blue screen. it references trixdp.dll i think it was, and then "begin physical dump of memory" i must reboot at this point. I use VLC media player, and exiting this program mandates a blue screen. Just now i exited mozilla browser and this was the first time i got blue screen from this program.