So I downloaded Roller Coaster Tycoon 3 and after that my computer's audio and video suddenly lags and slows down for a while then after that continues normally

Once I found that out I uninstalled it (shame for me ) And it still happens.. any one knows how to solve this?

(I dont know where to look for the specs of the computer but I do know that it's Windows XP)

EDIT: Found out the specs
Processor: Intel(R) Pentium(R) 4 CPU 3.00 Ghz
OS:Windows XP (Service Pack 3)
Graphics Card: NVIDIA GeForce G100

(Anything else just tell me)