Help, please! Why is my computer so slow?

I uninstalled the trial version of McAfee with just the McAfee removal tool (MCPR.exe). I can't remember the details but the advice was to just run the tool and nothing else.
I then installed McAfee Total protection 2010. I don't appear to have had any problems with it slowing my system but the product support stinks. It's coming up for renewal so I may go down the "free" route.

McAfee does have a site advisor which I find useful in avoiding suspect sites. I'd be interested in any views on this capability.

As for my original performance problem

The McAfee direction came out of your problem.

I like the "security" of the McAfee Site Advisor, but I have found that it usually only identifies sites that I would have thought were sketchy anyway

Rubbish. McAfee "Red Warns" some sites that on the surface look totally legitimate. "Grey" sites, including some obviously legitimate sites like corporate or government sites, just alert you to take a second look.

McAfee gets a real kick in the guts in this forum. I'd be interested in some balanced informed feedback on the McAfee site advisory function and alternatives.
(Not holding my breath).

As beta testers who became married to Win7, will always be biased toward the cleanest possible install with absolutely no performance hit - if this can also be achieved with adequate protection.

Win7 experts here in the most highly regarded forum nearly all agree that the paid AV's are bloatware which impact the OS too greatly for what they perform. They seem to bloat the system in proportion to how much they charge, as though they have to dance for their supper to convince purchaser they are busy working hard.

The OP got 8 viruses under MucAfee's paid watch and it slowed his system, none of the 100+ MSE home installs I've done have had infection or issue.

The free AV's we recommend seem to protect just as well if not better while having little noticeable impact on the system. When one steps over the line as AVG did, we wait for it to get back into performance graces before recommending it again. This is why without consulting amongst ourselves much, we seem to all come to the same conclusion.

My reason for considering dropping McAfee is due almost entirely on the expert advice that comes out of this forum.
My question related specifically to the site advisory function which I have considered a preventive measure prior to the role of virus checking.