Freezing

I have a Fujitsu Siemens 1ghz with 384mb of ram, and the
computer freezes when trying to load some of the most
basic things like, msn messenger and internet explorer.
Messnger does sometimes load , but after 2 conversation
windows the screen goes 'blocky' and freezes and i have
to shut down one of the windows. Resource meter reports i
have 33% free and it used to be higher before we upgraded
from 128 mb of ram. Our pc runs on pc-100 ram but the new
ram is pc-133 but we were told this would run normal, but
after installingthe ram there is no significant increase
in system performance. Any help would be appreciated,
sorry for the long stories!