Windows Defender was only a trial version and never a full version of a freeware for continued use. Dump it! It's useless at this time without the subscription to Windows OneCare. Norton is another "lost cause" explaining why you were seeing problems with AdAware SE Personal and others. It's a very demanding software and probably saw conflicts.
A much better antivirus tool as well as free are three different programs. The three top rated freewares are AVG 7.5, Avast, and AntiVir. The best retail program that easily dusts Norton and McAfee alike is Trend Micro's PC-cillin. You can run the 30day shareware to that find and clean stuff that the others combined will miss. In fact one sticky mentions Trend Micro's House Call which requires PC-cillin be first installed onto the system to run the free online scanner.
Another tool under review lately that has no conflicts seen with AVG, Ewido now known as Grisoft's AVG Anti-Spyware Remover another freeware and AdAware is recommeded by PC World magazine. Spyware Terminator. Both that and PC-cillin have been effective finding what Adaware misses while that Lavasoft utility finds the data miners missed by those. They work hand in hand there!
The links here are for the tools advised. First consulting the basic malware removal sticky seen at
http://www.computerforum.com/24782-basic-malware-removal.html You'll notice that some of this while still outdated at this time still lists House Call along with Panda. For the free tryout of PC-cillin Norton will be removed as part of the installation process. Afterwards you can remove the trial version for a good look at the others like AVG and ST. For House Call,
http://housecall.trendmicro.com/
AVG 7.5 and the other free spyware remover,
http://free.grisoft.com/doc/5390/lng/us/tpl/v5#avg-anti-spyware-free
Spyware Terminator is found at
http://www.spywareterminator.com/
AVG, Avast, and AntiVir are also found mixed in with a number of other freeware and shareware antivirus tools at
http://www.majorgeeks.com/downloads29.html Once you have given House Call a good run and replace the trial version with AVG, SpywareTerminator that also includes a personal firewall, and some other tool like AdAware you can post a HiJack This log to see if anything was missed.