Things get a lot messier then. First thing I'd wonder is did he add or remove some piece of hardware that may have caused the drive letters to change? Or did he try to change the system drive letter manually? Or edit his boot.ini file? Or go into the BIOS and disable that disk? Gotta try to remember what you were doing just before the error and give us a bit more to go on. Then again it may actually be a failed disk and beyond the scope of a mailing list. >No there is no floppy disk in the "A" drive or anything. > > My son has a HP Pavilion XE 744 with the operating system of Windows > > 2000. > > The problem is the only thing that will come up on the screen when you > > turn the computer on is the blank screen with the "Invalid System Disk" > > error message. - Users can unsubscribe from this list by sending email to 24hoursupport-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field OR by logging into the Web interface at http://web.tampabay.rr.com/spider1/24hrsupport.htm.