Losing my memory

[Etaqua]

I got this PC back in October, and it's recently started getting really poor loading times on Call of Duty.

Back when I first got it, the loading times on most maps was < 4-5 seconds, but now it's ~11-14 seconds.

It also managed to get 35-36s SuperPi times, now it is 42s.

The specs are:

A64 X2 4200+ (@240*10)
1GB Samsung Original (Changed from 2T to 1T, divider is 166, so still 200MHz)
GeForce 6600GT (567/1100)
MSI K8N SLI-Platinum
SB LIVE-24bit
200GB SATA Maxtor hard drive (Not sure which one, unfortunately)

This might not have any relevance, but the hard drive is 66% full.

I'd just like to know why it is doing this and how I could fix it.

 

[Etaqua]

I didn't think of spyware, and loading times are dependent on RAM with the rest of the setup as it is. SuperPi times are also partially dependent on RAM, although mainly the timings.

Defragging it done regularly due to pretty much constant torrenting; a quick analyse with the Windows defragging tool shows everything is contiguous as it should be.

I'm running NOD32 and Ad-Aware at the moment; if anything is found, I'll remove it and try again.

 

[Etaqua]

I ran memtest until it got to ~7200% (Around 7 hours), and it came up with 0 errors.

NOD32 and Ad-Aware SE Pro deleted all the malware they found on my computer.

I'm still getting high loading times though - although they are only 10s now - 1.5s lower than last night.

What else could be causing this?