Try closing programs first? I, too, used to have a 64-bit Windows 7 and an HP laptop (now a Lenovo one), but I only encounter this problem if I like play with a lot of other programs running at the same time. I guess it has something to do with the computer's memory.

It might also be "junkware" or pre-installed software that came with your PC that you may not be aware of and are running in the background, however I don't recall HP having too much junkware to be a bother. Try looking at your programs list or Googling your PC if it really came with resource-hogging junkware.

As for the compatibility settings, just run the game "as administrator". If you have a weak graphics processor, you can try disabling visual themes and desktop composition.

And I would as well advise using a crack as it somehow helped improve the performance of the game for me, especially with 2.0. In fact, most of us GTA: SA modders advise it. (And don't worry, it ain't illegal, as long as you're not using the crack to "unlock" and use pirated software that you didn't pay for.)