if its getting to near logon, its not a boot issue, so fix boot (which ensures key files are in place such as ntldr) and fixmbr (rewrite mbr) are unlikely to have an effect...
I Agree totally with TB!
I would try the following in order...
1, Safe mode - Didn't work in your case.
2, Remove/reseat all hardware. Chip creep not too common these days, but worth a go. Might be worth blowing out with a can of compressed air if very dirty! Don't forget to earth yourself by holding onto the metal computer case as you handle the hardware.
3, Remove all luxury hardware and leave the computer with bare components, ie: video/keyboard/hdd. you don't need any upgrade cards such as fancy secondary video,tv,usb, network cards to boot the computer!
4, I don't usually faf about with recovery consoles unless it's 2000/2003 server and i have 100's of gigs of data and 300 whinging users screaming down my lug holes! So as a home user i would go with backing up your data and re-installing XP. Failing that - if you don't have any method of backing up your data, go and buy another hard disk. You can then install XP on the new disk and slave the old drive as a spare data drive. Hard disks are quite cheap these days, for example i bought a 350gig disk over a year ago for £65, so 100gig now would be peanuts!
5, oh i and i forgot - one thing i like doing is resetting the bios and re-flashing if you can obtain an update. Not for the feint hearted as it can screw the whole pc up if not done correctly.
Hope this helps... let us know how you get on!