First off, pop up blockers suck. If you are using firefox (which you should be because if you aren't you suck) download two cool plugins:
Ad-Block Plus (
https://addons.mozilla.org/en-US/firefox/addon/1865)
No Script (
https://addons.mozilla.org/en-US/firefox/addon/722)
I also recommend Flashblock (
https://addons.mozilla.org/en-US/firefox/addon/433)
That's for FUTURE PREVENTION. The script block will prevent unwanted scripts from launching viruses and shit. It's a pain to use at first, but I have found that it is BY FAR the best firefox plugin. Especially if you like porn. Flashblock isn't helpful but it prevents annoying flash sites. And ad-block plus is by far the best ad blocker on the webz.
NOW: you need to do a few things.
One: download AVG (
http://free.avg.com/download?prd=afe)
this is probably the best (or one of the better) free virus scanners
Two: download Malwarebytes (
http://www.download.com/Malwarebytes...-10804572.html)
Three: Download Ad-Aware (
http://www.lavasoft.com/single/trialpay.php)
Four: Download Ccleaner (
http://www.filehippo.com/download_ccleaner/)
(I assume you are running XP?)
1. Boot into Windows, install AVG. This requires you to uninstall whatever virus scanner you currently have. Some people don't want to do that. If you have Nod32 or Kaspersky you can keep those. If you have Norton or McAfee you are an idiot and should uninstall them.
-uninstall current vscanner
-install AVG
-reboot
2. Install Malwarebytes, Ad-Aware, CCleaner, reboot
3. Start Windows up. Run AVG. Delete whatever comes up. Run Malwarebytes. Delete whatever comes up. Run Ad-Aware. Delete whatever comes up. Run CCleaners registry cleanup. Delete whatever comes up.
REBOOT.
Upon reboot push "F8" in the bios screen. Boot into SAFE MODE.
Once you are in safe mode run AVG. Delete whatever you find. Run Malwarebytes. Delete whatever you find. Run Ad-Aware. Delete whatever you find. Run CCleaner. Run whatever you find.
REBOOT.
I'm OCD. Personally, I'd go back into safemood and run AVG one more time. But that's me.
Reboot into normal windows. See what happens.
It sounds like you have a trojan that hijacked your we browser. Those are bitches. Those require extra work. If the above does not work your choices include
-manually going through the registry
-running a search for folders created/modified since your computer has been acting weird (and then looking for suspect folders)
-running a search for suspect files created since your computer has been acting weird
-manually going through your system32 and web browser directories
-checking your system processes through Task Manager)
and finally, if all else fails you can reformat.
good luck, post if you have any inquiries.