Possible Hardware Problem – Need Advice

hi i am having a problem with a PC – its a new machine (well reconditioned) i have installed windows 98 on the machine and then installed oracle reports, after the oracle reboot the system starts to freeze up and stop responding, i have tried the same with windows ME, and intalling office – but it seems after the initial windows install any other program seems to freeze/lockup the system – i have tried downloading all the windows patches from microsoft then installing some software but to the same result – could this be down to a hardware problem – such as the motherboard running to fast for the software or vice versa – i know i have come accross this problem before but i cannot remember what was causing this and how to fix it

any help would be greatlu apprieciated..

Thanks