just remove the modem then try it , it is sounding like a ram thing if you ask me , i had that a while ago it kept hanging , then got more frequent then it just refused to boot , it turned out to be a naff ram stick, but remove all your cards except the the video card , nics ect and then format the hd and re install , then put 1 card in at a time and run the puter until you find the culprit , if it happens with just the vid card in , it might be ram , try another vid card , but let xp find the drivers , good luck