You think you have issues...I have win XP pro on an AMD 473mhz processor with 152mb ram and I wait hours for updates and processes.
But seriously during a windows update you want to have little to no other programs running at that time, ie. exit AIM, MSN messenger, Kazaa, etc. or anything else you have running that need not to run for that time period especially since its going to ask you to restart anyways. Thats just to clear up some memory.
Secondly you could go in and upgrade your ram. That is usually the easiest way to get more power and see significent results instantly.
Lastly is the processor a true Pentium or is it only one of the Celeron processers that seem to me to run only half of the listed speed of 2.4.