@noiob did you switch from... I forget what is called, standard or compatibility mode, to acpi or vice versa? that makes most any Windows cranky, switching back can placate it
@noiob if you have the setup files for Windows on the hard drive, you can try an over-the-top reinstall that keeps all the drivers, programs, and most settings
most oems have them in c:\Windows\options\cabs
if you get an error saying something about you have to get an upgrade disk, delete or rename c:\Windows\win.com first and try again
@Mycroft a CD would work the same, right?
@noiob yeah, just running setup from the hard drive makes installation faster, and had the side benefit of never asking to insert the cd if you change any settings
if you can boot to dos with cdrom support, I recommend copying the cd's \winme folder to the hard drive somewhere (like c:\winme) and running setup from there (if a reinstall is what you want to try)
... it might be \win9x instead, it's been so long...
@noiob ah, I just remember that being a setting in older pcs that would cause Windows not to boot if it was set to something other than the setting Windows was installed under
good luck