There were several blue screen errors before it started saying Invalid System Disk. It's a HP Pavillion, very old like maybe 8 years or more, ram is 515 mb.
I confess to mucking around itside of it before, which caused some errors, but never this one.
Also, I took the drive and put it on my computer as a slave and was able to access all the files on it without any problems. Does this mean there is something else wrong than just a Windows system file error?