Slow computer - malware?

[Fiftyeight]

Hi. I'm new, and way out of my depth here, but here goes.
My computer has been running slower for a week or two, and I thought it might be malware. Having stumbled tonight onto the MajorGeeks site, I worked through the Read and Run Me First Malware Removal guide, but without complete satisfaction, though I did delete one suspicious item. I didn't really know what I was doing, just followed the instructions. All seemed to be going well, until I got to the RootReplace software, which crashed on my computer running Windows 7. I couldn't open rar, but I again downloaded it in zip and it opened but didn't work. (Hope you get what I'm trying to say.)
I kept going on the advised procedure, and saved some logs, but I think I can't post them here, so I don't know what to do. I've never been on a forum before.
I'm not sure how to best describe my computer, but here's some info.
AMD 64 processor 3000+ 1.81Ghz. 4 Gb Ram. Windows 7.
I'm now stuck with a computer that has AV disabled and is no faster, and I'm not sure if I helped by trying, or made things worse.
Please can someone advise me what to do next?
Please be patient. It's 1.52am her in Australia, and I just have to go to bed, but I'll check tomorrow for any comments. Thanks.
Fiftyeight.