If your once zippy computer now likes to run slower than the proverbial molasses in January, it may not be your system's fault. As software is updated, there is generally an increase in its bells and whistles. This doesn't come without a cost: among other things, this often means that the amount of RAM required to run increases. Unless you're in a position to keep adding memory to your machine, you may have to just live with its new-found sluggishness. Unless you can figure out a way to convince your new version to curb its appetite, you might as well just go get another cup of coffee. Or you can try Minimem on for size.
This tool tries to help you run your apps with the smallest amount of memory possible. It does this by regularly checking which processes are actually doing something, and removing the other ones from RAM. When you need those formerly idling process back, they're just loaded again, and you're on your way. In the meantime, you've got your memory back to use for things that are really happening right now. This can help you with big apps, as well as smaller applications that may have some nasty memory leaks (it's not a bug, it's a feature). Along with helping you with not-so-optimized applications, it can also help breathe new life into your older hardware.
Minimem is free for personal use. It's a Windows application and should run under just about any flavor of Windows, although it's been tested mostly under XP.