Deleting from a command prompt isn't going to be easy and is probably left well alone if you aren't confident in its use, which it would appear you aren't. Paths with spaces usually have to be wrapped in " quotes " however this isn't a workable option from the command prompt if I remember rightly. I haven't used win98 in about 5-6 years, but the 8.3 thing rings a bell so C:\Windows\Downlo~1\ is the usual way to overcome a folder with spaces by shortening it to 8 characters the tilde ~ being the seventh and 1 the 8th unless you had two folders the same and it would end in ~2.
Directories with spaces should be just as accessible as those without, using windows explorer (rather than a command prompt) and navigate the path.
I would rather leave the crash during scanning and deal with what is more important first.
Have you tried the two programs I suggested, SAS and MBAM (last two links) I think they work with win98 though you would have to check.