Just a few ideas to try.
Put the CPU/Memory monitor gadget on to Vistas sidebar.
A clean install of Vista (that means Vista and 'nowt else, just Defender for basic protection) should idle at only 1% or so use.
How much RAM have you ? With 2gb, a 32 bit Vista install should be using only around 25% RAM.
IE should open instantly. If you have issues web browsing maybe the problem lies elsewhere.
Have you run,