Here's what I currently do for security (and to try to keep crud from building up in the Registry)

1. Am running Microsoft Security Essentials (have tried the other freewares, and even though I didn't want to like it, MSE gives the least performance hit by far)

2. Every time I uninstall a program (and once a week anyway) I run CC Cleaner to cleanse the Registry and the detritus from programs (temp files, etc.)

3. I run SpyBot Search and Destroy once a week, and also have its TeaTimer function engaged along with passive immunization (I am also using their .hosts file to divert crapware calls)

Even thought my ThinkPad x100e (Windows 7 Home Premium) is speedy for its form factor, I want as little overhead in terms of services, etc., but not at the expense of security.

Is the SpyBot routine overkill? Ever since starting to use MSE, Spybot very seldom finds any spywares.

Any other suggestions?

Install Ubuntu. It will double your speed and reduce security risks to almost zero. It can setup a dual boot for windows if you want.

Thank you, but that really isn't going to be an option here.

Sounds pretty much like my routine. I used to run Spybot, Adaware, and Spyware Blaster regularly, along with CCleaner and NIS 20XX, but after at least two years of finding nothing but cookies I'm down to NIS and CC, along the Linksys router's protections.

This sounds pretty normal and about what I do. I actually add a bi-weekly scan with malwarebytes to the mix and I use web root spy sweeper instead of S&D since I found that it picks up slightly more stuff and the run time overhead seems negligible. No issues in years.

Sounds normal for anyone using IE
I find Spybot S&D to be useless when you are already running Malwarbytes & a Top Rated Virus/malware program. CCleaner is a good bi-weekly run.
Of course none of this is matters if your not updating them weekly at a minimum.

Threads like these make me glad I do not waste countless hours trying to find and delete viruses and spyware from windows.

sounds like overkill to me. All I do is daily MSE scans. I also fully re-install Windows every 6 months just to keep things fresh.

As always, the prime source of spyware and visruses is yourself - keep your OS up to date, don't download stuff from weird locations and avoid crappy browsers like IE.

Lemme guess - you use a Mac?

The steps the OP outlined are not "countless hours". With the exception of running CC cleaner, it all happens behind the scenes and scheduled. I spend no more than 5 minutes a month on my AV/spyware software.

No Mac here. Two old Dell laptops running Ubuntu. They run faster than your Core i5s with all that AV/spyware running in the backround.

I'd call it a bit of overkill for a cautious, savvy user. Spybot S&D doesn't work nearly as well as Malwarebytes these days, and I've found TeaTimer to be intrusive. On my desktop machine, I run Norton AV 2010 behind a good hardware firewall/router (Netopia ENT-3386), and every other week or so I run Malwarebytes. I also have a modified HOSTS file to speed up page loading. On my laptop (dual-boot Vista Business / Windows 7 Pro) I run Microsoft Security Essentials.

Oh, I do keep a desktop computer, separated on its own VLAN, that I use to try risky web things or run risky programs, and I sometimes mount other hard drives in it to scan them (e.g., they have a Trojan or virus that prevents them from booting or running normally).

If it's working for you I say stick with it. Teatimer brings my machines down to zero speed and 100% utilization, so that wouldn't work for me.

The spybot on top of the MSE may be a bit overboard for a normal system in non high risk use, but if it's working for you I say stick with it.

I am completely opposed to using any program that requires itself to be continually running in the background for AV / security. I haven't run any in at least 5 years and have never once found anything even remotely suspicious on any Windows PC I run. I do one-off scans every few months as a precaution but I've yet to come across anything to be concerned about.

The number one priority has got to be to stop running IE. With a modern OS (eg: Win7) plus a modern browser such as Firefox, you really have to go out of your way to let any sort of spyware get onto a PC. A few generations back (XP / IE7 / FF2) I'd only recommend this approach for people who were very aware of what they were doing, but these days I think the situation is somewhat different.

The performance drain caused by any of these "active" scanners is still simply too great, even on a relatively high-performance machine, IMHO.

Which is quite different from not having a nice collection of nasty stuff on the hard drive, of course

But you have a point in the fact that you COULD have a nice collection of nasty malware even with a continuously running AV.

I don't get your point - I certainly don't have a collection of "nasty stuff" on the hard drive. Nor do I see why you view it as "different"?