im afraid i wont be much of a help...

well the story is as follows:
i got a message from the firewall telling me if i would please to let a remote equipment acess to isass.exe on mines... (and keeped going until i automated the block access task)

I didnt managed to know exactly what isass.exe is... but there are lots of threads of ppl saying that it messed its computer, specially on boot(which seems one of its related tasks) (i think i sawd a post signed with the "thanks, brian" characteristic of yours on the end on one of those threads?), noone seems to know how to fix it and it seems that installing xp over the old one doesnt works... so my advice is "get a up-to-date firewall that blocks the access to that file"...(and the advice of the threads ive seen is format frist...) (toldya cause i have learnt to regret not having it installed on my "i want all the possible power" XP build on the other disk, then forgetting to disconect the internet...