did I just give away my information?

So this balloon pops up on the toolbar telling me that my computer has been infected with spyware, and to click here and windows will download the best antispyware thingy to get rid of it. in my infinite naivety, i clicked on the balloon and downloaded a thing called "PestTrap" and it checked my computer and said I had some spyware, but I should give them money so they can remove it for me. It directed me to their website, where I entered my checking account info, the last four digits of my social security number, etc. however, it told me to try again later. i got frustrated and downloaded another antispyware thing that told me PestTrap was a spyware. So I clicked on the delete spyware button, but the AOL spyware center just told me that it found PestTrap still on my computer. So now I'm wondering if PestTrap still has my info, and how long it'll take them to take my money. Like, do I still have time to go withdraw it all from the bank? This happened within a half hour ago.

 

how exactly would i go about cancelling this check? i entered the information on a web page. do i have to go to the bank to do that? I really only just got a checking account, and i'm not sure what to do.