ummmm....well i dont know much about fixing computers, but when i had a big problem with windows98 and my compuiter wouldnt even boot right, i deleted 98 off my computer fully then installed it again. now it says theres a bunch of .dll files missing upon startup, but it runs and all my programs work.
i was able to use command prompt for all this. like the thing where you type
c://setup and all that junk.
SO, in conclusion, just reinstall what worked - xp. or get windows 98, b/c this computer has 128 ram 500mhz and it works good with it.