Gta san andreas blocked by vista.............

Hello,
Hello,
I am vinay. I have a studio 15 lappy.
It has windows vista home premium. I had installed gat san andreas(full version from original cd) in it. it used to run smoothly in the beggining but after a week,vista blocked the game execution and also the batch installation of gta san andreas. same is the problem with my friend's lappy which is a hp dv6. I run the game on my computer in windows xp.I think vista is creating problem with batch gile installation of gta sa , and also with gta game execution. The game is original and full versiuon not demo.
My lappy's configuration is more than eough to even run the gta 4.
Plzzz tell me the solution to run the installaion and the game.
plzzz reply