Take a look at Black Viper
. The page lists the various services that are installed and gives an overview of what the service does, what services can be changed from Automatic to Manual to Disabled.
I guess a seperate login could be created with the modified services for gaming. Not sure though but it couldn't hurt to try. I would create the login, change one service and see if it applies to just that profile or all profiles.
At any rate the individual claims that 5 - 70 MB of memory can be reclaimed for gaming. Don't skim the page, read each line, it appears a good deal of work went into making sure all bases were covered.