hi, did you upgrade to Vista yourself or did the pc have it ready installed?
'bad pool caller' as far as i can recall should have nothing to do with hard drive/mobo/ram, although it would normally be seen after new software/hardware has been installed.
Vista is still a long way from full compatability (hooray for new OS's) so unless it was pre-installed i would advise going back to XP (or whatever you had)
or, give this a try....it is a link to microsoft website 'fix' site.
http://updatemicrosoft.fix-xp.com/index.php?key=Bad+Pool+Caller&t=3N100A1C&gclid=COmT_4iDppQCFQs4QgodNRjLuA
ian, July 2008