Which anti spyware/malware remover is best?

A little while ago my web browsing came to a dead stop. My ISP suggested I had some malware. I was astounded because I've been running Outpost firewall and had thought it was doing a good job. So I ran Spybot S&D which found nothing of significance. I then decided to download Spyware Detector.

After quite a lengthy scan, it found 7 spywares and 300+ "threats". The spyware included:
Trojan.Dumaru
Adware.Deskadtop
Adware.POP A
Adware.Mirar
KeyLogger.EMCO
Spyware.Guardian

I decided to test this against some others.
Trend Micro Anti-Spyware found nothing at all.

Spybuster found some problems but wouldn't give a list to see what it had found.

CounterSpy found
SearchNugget, DNSCatcher
ErrorSafe Rogue Security Prog
+ 12 cookies. This trial version actually allowed me to delete 2.

Pest Patrol from eTrust found problems but wouldn't list them.

XoftSpySE found:
BonziBuddy
Cyberspy
PigSearch
Sfonditalia
Adwareloader
Viewpoint.

Those that wouldn't show me a list were reporting between 7 and hundreds of "problems". I assumed that these were all actually finding the same ones and that they were just different names (as anti-virus programs often report a virus with a different name).

So, because XoftSpy ran so quickly and didn't seem to want to take total control of my PC, I decided to pay them the money. I removed all the malware it found. I then cleaned my Registry with another cleaner.

Then, before I removed everything else from my PC, I decided to run Spyware Detector again.
You will understand my frustration when I discovered that it was still finding 7 spywares although the "associated threats" had been reduced slightly. I was so annoyed with myself for wasting money, I just went ahead and paid for this program as well.

So after removing all the nasties, my PC has been running like a dream. It just zips along - I had forgotten how fast it used to run. I disabled the annoying popup from Spyware Detector. All seemed fine.

Then yesterday, I came across a great long list of spyware removers, many I had never heard of. I decided to try out Spyware Seizer. You will know how exasperated I felt when it found dozens of tracking cookies, a file called hkcmd.exe which it reported as Backdoor Spy.Delf.abb and 4 trojans in the registry. Before I could get to this list, it was being very heavy-handed with popup errors telling me that I had serious errors with things like notepad+ (my replacement for notepad) and my homepage setting (which it wanted to set to blank) and my scanner or the twain driver, and several programs which sit in my system tray. It took me quite some time to get it to ignore all the "errors".

Nevertheless, seeing a backdoor trojan was worrying. I re-ran both my "paid" antispywares and they could not find the same problems. I then did a Google Search for hkcmd.exe and found references to this legitimate file.

So, have I wasted my money? Which anti-spyware is really the best? Why do they all seem to report different malware? Why do some report dozens of cookies, others only a few, and some find no cookie with problems?

Your advice would be appreciated.