spyware strike version 2.5 has downloaded itself onto my system.it has taken over my internet explorer homepage taking me to www.securitywarnings.net even though my home page on start up says something else.it has also put a symbol in the bottom right corner that flashes up a big box saying system intrusion detected i use spybot,adaware and avg virus.i have used the spybot to get rid of it but it cant.i have no knowledge as to the workings of a computer so vany help would be greatly appreciated

If you follow the instructions here, ( you may already have some of these programs )

http://forum.ccleaner.com/index.php?showtopic=3505

and then post a hijack this log in the hijack this section of the forum.
One of the resident experts will help you as soon as they can.

Discussion and removal tool Here.

Its better to post a hjt log just in case the infection caused other ones as well.