The hard drive on my Toshiba c55d laptop died. I replaced it and made changes in the BIOS to let me install Windows. The forum gave me the info to make the BIOS changes. I decided to start with WinXP. Got through the initial install, to the point where it will boot with the WinXP logo and go to the XP setup page where "Installing Windows" is highlighted and "setup will complete in approx. 39 minutes". The "Installing Devices" bar gets to half completed (about 35 minutes remaining), when I get the Blue Screen of Death and a message "IRQL_NOT_LESS_OR_EQUAL". The screen suggests disabling or removing any new hardware or software or changing BIOS settings for memory shadowing or caching. I can't do much with the suggestions, since the hard drive is the only changed hardware and there is no software except the partially installed XP and there are no memory options listed in the BIOS. I've tried to use the "repair" function to no avail. Tried to install from a "safe mode" start, also with no effect. Tried a "clean" re-install, where the single existing partition that Windows is loaded into is deleted and the install is begun from scratch. No help. I even tried to use my Win7 installation CD, but the existing XP will not allow it. When I try the Win7 CD, I get a box that says I have to insert the XP CD to proceed. Since I don't have a fully functioning OS, I don't have a way to go in and re-format the hard drive. I can only re-format/delete the partition under the partially installed WinXP. Nothing I have tried can get past the point where about half of the Windows files are loaded and about "35 minutes remain" on the install screen. Every time it gets to that point, I get the Blue Screen Of Death. I've gone back into the BIOS and changed settings I previously had to modify in order to get the system to even boot, but going back only prevents the unit from booting again, so I have to return them to what I had previously used. I'm stumped and stalled out.