But you write you tried everything so did you go get HIJACKTHIS to create a log file then proceed to understand each line in the log file then ask others or google the lines you didn't understand?
I've done that too many times and found odd things, conflicts in software (Teatimer being one of the more famous ones) and more.
-> In parting. You may not have downloaded anything new but those security apps, Microsoft do that for you.
I suddenly find I can't open any .jpg, .bmp or gif files and I can't open some .doc files too. Nothing will open any pic files I've tried Windows P&F Viewer, Irfan View, Fireworks, Windows Media Player, Internet Explorer etc. etc. believe me I've tried everything and nothing will open them. Some report "Unknown file type" some report "cannot read header" some "preview unavailable", I've hundreds of files collected over the years and the problem began a couple of days ago. I've checked the file associations and run all my security softwares and everything reports OK. I've not download and installed any new programmes recently. Operating system is Windows XP home version SP3. Has anyone any idea what may be causing this problem please and more importantly how to put it right?