Why is my computer slow?

i have dial up,defrag every week,use disk cleanup every week,use AVG antiviris,spyware bot for antispy,i have 88% of free space available and still my comp is slow,whenever i try to exit out of a page it freezes then says internet explorer has encounterd a error,has to close.Anyone have any ideas,pls help

Why is my computer slow?anti virus protection

1)Stomp auto-starting programs. Click Start %26gt; Run and type "msconfig" at the prompt. Click the Startup tab and look at all that junk that loads when you launch your PC. Do you really need "Adobe Reader Speed Launch"? Probably not. Turn off anything else that looks useless, but be careful not to disable Windows system components.

2) Clean up the disk. Uninstall unneeded programs (especially those that run at startup and/or put something in the system tray), run Disk Cleanup, and defragment the drive. This is a good first step that will almost always take a few seconds off boot time and application loads for any computer.

3) Run a full anti-virus and anti-spyware scan. I would recommend using AVG Free Anti-virus, AVG Anti-Spyware, Spybot, Ad-Aware.

4) Clean up the registry. This is controversial, as some experts claim registry cleaners don't really help. I've seen evidence to the contrary, so I recommend doing it if you've got a major slowdown. CCleaner is free and worth running.