If you PC boots up that's good news. It sounds like it's having problems checking the hard disk, this could be just a glitch or a warning sign. I'd strongly suggest backing up your important documents, just in case.
Does you hard disc make any unusual whining or screeching noises? If so it might be worth running error check on the hard disk.
Have you added any hardware to your PC - such as an additional hard disc or DVD drive? If so you might have disturbed one of the cable.
There are various tweaks you can make in the BIOS (or setup) as neildownx suggests. If you're not sure what to do, dig out your computer manual and look up the BIOS setup.
To get into the BIOS wait until it has checked the IDE drive (it'll say something like checking IDE drives ...done) then press F2 about twenty times. You might have to try this a few times to catch the right moment. You should then be able to enter the BIOS Setup and look for the Fast Boot setting.
There are other useful maintenance tips for when you've got the system to boot up.
CCleaner, originally called Crap Cleaner, can be downloaded from
FileHippo.