Not W7. You don't have enough hardware.
Just re-install XP and it should get fast real quick - and cheap. Use free CCLEANER from
http://www.ccleaner.com but when you install, DO NOT install the Yahoo toolbar crap. Just accept the defaults for everything when you install and when you run it.
The software is EXCELLENT. Run the cleaner, then fix your registry. You can also stop the automatic startup of a BUNCH of crap that inserts itself and wastes CPU. Just be sure of what you are disabling. A couple of things are from Windows and are necessary.
We use it on ALL PCs here, 30 or so, and it really makes a difference.
ALSO, if you want to see HOW FAST it CAN run, try free SPARKLEXP, which installs another "user" on the system where NONE of the unnecessary crap loads. Get it at
http://download.cnet.com/SparkleXP/3000-2094_4-10730157.html. It will give you some idea of what the PC can do when reloaded. Even better if you run it AFTER cleaning the system with CCLEANER.