Trojan's i cant get rid of

Hello
I am running windows xp home 2002 service pack 3, Intel Pentium 4cpu, 2.80ghz, 2.81ghz, 512 mb of ram.
I came home from holidays and my computer was full of trojans and worms via personal anti virus, i thought i had cleaned it all out and have downloaded anti virus protection via your website, BUT each time i download and try to run them it comes up with an error message asking me to send to microsoft and wont let me run them. I can however run AVG and Avast. but i downloaded spybot, assasin and spyware doctor and they all give me the same message. DOES THIS MEAN I STILL HAVE VIRUS IN THE SYSTEM AND CAN SOMEONE HELP ME FIX IT!! NOT VERY WISE WITH COMPUTER LANGUAGE OR WHAT TO DO....ALSO WHEN I GO TO MY GOOGLE HOME PAGE IT KEEPS ASKING ME TO RESTORE THE HOME PAGE AS THE LAST SESSION WAS CLOSED UNEXPECTEDLY. If someone could help me with a remote session or talk me through what is happening i would much appreciate it.
Thanks for your time
Itsracey :confused

 

Ps: I have tried running the read me and run first
but the computer will not allow me to run any of the programs after installing, i get all the way to installing tools and running scans and thats it