When Windows fails to boot it is normally caused by you installing a program or device and it has caused a conflict with one or more other programs. This will no doubt give you plenty of heartache if you're not certain which program caused Windows to not boot up.
If you recently installed a program or application and know where it was installed, you may be in much better shape as for as correcting the error. Here are common ways to correct the problem of your computer not completely booting up or not booting up at all.
If your computer will not boot-up at all, hopefully you have made a good emergency boot disk. You can always make a windows startup disk by creating one from another computer running Windows 98 or Me. Perform the following if your computer........
Won't Boot-Up At All
FIRST: Put your boot floppy disk in the floppy drive and turn on the PC. On some computers, you may have to access the bios and select the Boot priority to your A: drive. Save any changes and select "Start Computer without CDROM support" and press Enter. Once you are at the A> prompt, type dir c: and press enter.
If your programs and other files are present, try restoring your system Registry by following the steps below. This may repair Windows, the Config.Sys and autoexec.bat files to where the PC may boot up normally. When the files are present, it’s a good indication of a good hard drive.
SECOND: To correct the problem of your computer not booting up, type in "fdisk /mbr" and press Enter to restore your master boot record. Type "Scandisk C:" to check the hard drive for errors that have occurred. You can also type "Sys C:" to hopefully restore files needed to boot up your computer.
THIRD: If the above procedures fail to repair your computer, you can repeat the first part of step one above and select "Start Computer with CDROM Support" re-install Windows.