First you need to find out where it's stemming from:
A.) A website you are visiting.
B.) Adware installed on your computer.
What I would do:
1.) Take note of what sites you are visiting when the popups appear.
2.) Before closing the tabs, see what websites they are linking to.
3.) Scan your system for malware. You can click here for some free options.
I upgraded to Vista Home and now when I start IE, I get multiple tabs with software offers and such. Can this be stopped?