to speed up your system
go to system tools cleanup disc and defragment also running anti virus will help.
blocking popups depends on what system you have click on help and support and type in blocking popups
to block popups try installing the google toolbar. just search for it on google.
to fix the slowness of your computer, download adaware and let it scan and remove all the threats it finds.
The most important things you need to get are: Scotty (Make sure it is on patrol), Norton Protection Centre, BT Yahoo! Online Protection, (if you have got BT Yahoo! Broadband that is), BT Broadband Desktop Help, (Which you are likely to have), Safety Remove Software and that is really it.
When the pop ups if you want to enter it just click temporary allow pop ups if you don't want it just leave it like that the browser will automatically block it!
All you have got to do is go into Internet Options > Privacy and tick the pop up blocker. In the settings you can allow or not allow what you want.
However having said that NO pop up blocker, browser or an independent program is 100% efficient in stopping them. The people who "send" them keep changing bits in them so they slip through because they are not detected.
Bit like spam. You block it or filter it and it still gets through. It's because, as I said, they make small changes like spacing, characters etc.
When the pop ups if you want to enter it just click temporary allow pop ups if you don't want it just leave it like that the browser will automatically block it!