vista enterprise now vista ultimate

for about 2 months my wife and I where running vista enterprise and
loved it, but it was only the 90 day trial. I finally installed my
ultimate "clean install" on both pc's my wife and I have the same pc's
w/ 3.46 pentium 2gig memory and 80 gig HD and I notice the ultimate is
running slower than the enterprise. is there anything that you guys can
think of for me to check to speed it up? I ran my regcure, regvac and
system mechanic 7 and we both notice slowness, when opening programs,
installing or just starting up and it my startup I only have the
following. win defender, avg pro 7.5, sidebare and logmein.