I'm a bit confused here. Is the reason you can't use system restore because there are no restore points available or is it because the system restore window is just a blank window? My understanding is the latter. If the restore window is blank it doesn't necessarily mean there are no restore points available.
Can you boot to safemode (I realize you can boot normally)? If you can, boot to safemode (log on as administrator) and try system restore from there.
Have you tried the last known good configuration in the startup menu you get when pressing F8 while booting. It might not fix the problem but you never know.
Also, am I understanding you correctly that you don't have a regular windows disk available? If not, have you ever used the restore disk before? It's possible when you boot from it, it may give you the option to reinstall windows besides the option to restore the computer. I'd have a look.
Do you have SP2
installed yet? You could always try installing that to see if it would patch things up. Not likely but you never know. If you have to wipe the disk anyway, it would be worth a try.
These suggestions are just shots in the dark on my part. I really don't know if any of them will get you anywhere but if you haven't tried them yet, it can't hurt given the alternative.