a good antivirus would solve it :P

Your internet browsing speed has very little to due with the computer hardware. You may need to upgrade your internet service through your service provider.

For the pop ups, i recommend using firefox and not internet explorer. Also, run antivirus and a program called Adaware which will clean your computer.

First of all, and this is rule #1. Be very wary about installing more software to speed up your computer. Because it is software that bogs down a computer, you should be very hesitant about installing yet more in order to help it. Only install programs that you absolutely trust.

Clean out your internet temporary files (tools-->options).
Search for and delete all temp files on your hard drive "*.tmp"

Double click the my computer icon and run a defrag on your hard drive. Make sure your drive is not compressed (this increases time to read/write files)
Cleanup your disk by using: Start/All Programs/Accessories/System Tools/Disk Clean-up

Boot into safe mode (press F8 during the boot up) and disable unwanted services that may be starting up with Windows.

Open up the programs that run when windows starts, and look for a place to disable them from startup. Some applications may say "run in taskbar", this is what you do not want them to do.

Add more memory. While this is certainly an option that costs money, it is by far the best thing you can do to increase computer hardware performance for minimal cost. Adding RAM is the best "bang for the buck" you can do when it comes to improving hardware.