If you do a have a fairly literate computer person around, ask them to create a different "Hardware Profile", it's kind of like another user account but more powerful, and you'll need to create a different user too.
Go into the control panel and depending on your view get to "system properties", then choose the "Hardware" button, then choose "Hardware Profiles", choose your current profile and then choose copy, then rename the copy you made to "Games" or whatever, so you can see the difference when you choose it later. Also choose what happens when you start, if you want it to boot the default after 30 secs or to wait for you to make a choice.
After you've done that u should also make a another user account. I've made a new user account called "Simmer".
Now, this is where you need the computer literate person, open "services.msc" and start choosing which services you need for that NEW "hardware profile". Choose a component, right click and choose "properties", choose the "Log on" tab, then in the profile window choose the new profile and then click the "disable" button to stop that service from starting under that profile.
I don't use the internet on my games profile so i turn off most of my network services and my firewall and i only open files that i've downloaded for my games so i turn off my antivirus. I only install things on my default profile under my normal user account. I don't burn CD's with that profile so I disable the Imapi CD thingy. No internet access means the Autoupdate thing won't work so i disable that and the antivirus autoupdate.... so on and so on
And yes, get cacheman. I have 784 (?) megs of memory and cacheman reports i have 485 free on the default profile on my default desktop, but it reports 610 free on the games profile with the "simmer" user, and i have the simmer desktop set at 800x600 so i can tell the difference between the 2 different log on screens.
"CAUTION"!!!! User account changes don't affect hardware profiles, so don't use your default user account on your modified hardware profile or things might not work right when you boot into your default hardware profile with your default user account.
So for me, "Simmer" only logs in on "Games" profile and "Default" only logs in on "Loaded" profile.
There is quite a bit of info around the internet about services that run with windows and which ones are neccesary, so get your helper to look for info if your unsure about something...
Good Luck and PM me if you have questions or need any help