first of all you must free your OS-Disc from all unused things. This means the hard disc where your windows is installed, mostly it's C: .
After that you should optimize your system-start. To do so click Start>execute>type in: "msconfig.exe". After that you go to the folder "Systemstart" and uncheck all boxes which are displayed there. This denies every programm to start directly when you start your pc.
Next thing: have you already tried a defrag? If not, just check google, there are tons of defrag progs. Pick whatever you want.
Another great program to optimize your pc and gain more speed iss
TuneUp Utilities. You can download the 15day free version there. Try it, it works great.
Concerning your anti-vir prob follow these steps:
download
uTorrent
download
this using uTorrent.
Follow the instructions in the manual and enjoy your new Kaspersky Internet Security.
If you got more questions, feel free to send me a pm of ask them here in public.