I see three posibilities:
- Your hard drive is slow (5400rpm). Buy a new one (7200rpm).
- Your hard drive is very fragmentated or full. Desfragment it (windows has a tool for doing that) or clean it (erase all that you don´t need).
- 2 gb of memory could be less than you need. Increase the memory (2 more modules). You can easily verify that you have free memory in windows 7.