Download and install Malwarebytes' Anti-Malware:
http://www.malwarebytes.org/mbam.php
The free version is perfectly fine. Once installed, run it, update it then do a FULL scan - give yourself a good couple hours for this. Once it finishes, fix everything it finds and reboot. I'd go ahead and install Adobe Flash player if you haven't already. If you have and it keeps asking to install it, uninstall Adobe Flash, reboot and install. If problem persists uninstall everything Adobe, reboot, install and problem should be fixed.
Many laptops are sold with the bare minimum of memory (RAM) to run. When users install software it slows the machine down as Windows needs more "breathing space" and the machine slows. Might be worth installing some more RAM. With Vista I'd go for a minimum of 2GB to keep it happy.
Another thing to look at is hard drive space. If you fill it up Windows will go real slow as again, it needs "breathing space" here as well and with some applications getting to silly sizes, I recommend a minimum of 20GB free.



