I'd start with adding 1 Gb RAM, so you've got 2 Gb in stead of one. That should make a noticeable difference. Then disable Aero (http://www.howtogeek.com/howto/windows-vista/disable-aero-on-windows-vista/) to see if that helps.
Then go into Task Manager, and tell what processes are using the most CPU (say, the top-5) while you're doing something (tell what!) that you find so slow.
please can some one help me, my computer is so slow
Processor:Genuine Intel(R) CPU 2140 @ 1.60Hz 1.60 GHz
System:windows vista home premium 32-bit
it has 2 hard drives 69.7 GB and 69.5 GB I have used 38.7 GB
ther are not put a lot of programs on it i have put on,
the program for my printer by hp
daemod tools lite
abobe flash player 9 activeX
sim city 4
if any one hase advive please help