Well, that eliminates using System Restore or XP's Recovery Console. I suppose if you had a Registry Backup, you wouldn't be asking how to fix your registry, so thats not a likely option either. Oh, well. There are a few things you can try. From DOS, at the "C:" prompt, enter, without the quotes but with sthe space before the slash, "scanreg /fix", then hit Enter. If that works, wonderful. If not, 98 actually should have what amounts to a Registry Backup. It can be employed from DOS as well; at the "C:" prompt, enter "scanreg /restore", again without the quotes, but be sure there is a space between the word "scanreg" and "/restore", then hit Enter. You should be presented with a choice of backups which should represent the last 5 times the system successfully booted. They should look something like "RB00x.*", where "x" is that backup's position in the sequence, and RB000.cab should be the most recent. You may have to try a few before you hit one that works. Note: you can go right ahead and run these commands from the "C:" prompt; you don't have to be in the C:\Windows\Command folder.
When you get things sorted out, have Windows make you an emergency boot disc, and learn how to back up your registry to disc, and keep a frequently updated registry backup handy.
And, of course, a full OS install disc is always a good thing to have. "When all else fails ... " is about when you realize you should have been a little more diligent with your backups.