My computer's got a real problem with adware at the moment. I use Ad-Aware, Spy Sweeper and SpyBot which seems to delete hundreds of affected files. However, each time I restart the computer and log back online, all the deleted adware returns. The most virulent seem to be "Media Access", "PowerScan", and "GB Dialer". Any clues on how I can delete them and ensure they will not return? Thank you!!

You should check your phone bill from what I've read about GB Dialer!
Here's what i think you should do:

Is your Anti-virus program current and updated? If not you can download a free anti-virus program here (US Link): AVG Free
When you have downloaded and installed it you need to go online to register it and update it. (It will probably prompt you to do this.)
Once you have installed AVG uninstall your old Anti-Virus software because you should only have one running on your system.

Do you have any anti-spyware installed? If not download and update all of the following:

• Ad-Aware SE from http://www.lavasoft.de/
  There is a tutorial on how to run this here: Ad-Aware Tutorial
  
  
• Spybot Search & Destroy from http://www.safer-networking.org/index.php?page=download
  There is a tutorial on how to run this here: SpyBot S&D Tutorial
  
  
• SpywareBlaster from http://www.javacoolsoftware.com/spywareblaster.html
  There is a tutorial on how to run this here: SpywareBlaster Tutorial

Reboot your computer in Safe Mode and run the anti-virus scan and anti-spyware scans there.
If you are not sure how to boot in Safe Mode there is a tutorial here: Safe Mode

If running these scans is not successful then you need to submit a HijackThis (HJT) Log to the malware experts here at BC:
To post an HJT log please read the pinned posts 'How to use this Forum' and 'How to post a Hijack This log' at the top of the forum:
http://www.bleepingcomputer.com/forums/Hij...alysis-f22.html

hth

Very often, running your malware removal applications in Safe Mode (always off-line, of course) will make them more effective. Check to see, moreover, if any of the files they find are hiding themselves in your system restore files. If so, temporarily disable system restore (you will lose all restore points), rerun the applications, and then re-enable system restore and set a new manual restore point.
Regards,
John