i had the same thing happen on my old computer, try booting in safe mode, copy all the needed files to an external hard drive, and reinstall the operating system. than if u need download all the drivers.
i decided to reinstall windows as i thought it was going to be easier but saying that when i reinstall windows and when it copys windows files to HD it shows the blue screen this is the code that appears;
mmm... i got a problem when i try to reinstall windows (delete the old partition and install windows on it) it comes up with the same blue screen error the 0x050
you can use this to test your memory. Unpack the zip file, then burn the iso to a cd and you can boot from it.
you can check your harddisk using chkdsk in your command line, but i forgot how you can get there with the xp installation cd.