Ressolving and getrid of antispyware"virus...

Question

hi I am using win XP SP2 in my system. i am using avg 7.5 and Mcaffee 9.0 in my system. usually i download latest versions online. recently unexpectedly "virus heat.com" antispyware website is downloaded intensionally into my system and making my internet explorer as default without my knowledge. it is alerting always and intensionally opening itself. I am fever about it and requesting you give me an idea to get rid off from this problemprakash