Step One: Your Recording Hard DrivesOne of the first things you should consider getting for your recording computer is your hard drives. If you've got the resources to do so, I highly recommend a second hard drive -- internal or external -- to only use as a recording drive. This hard drive should do nothing more than store your recording files, which are accessed on this drive. The faster the better -- a 7200 RPM drive is highly recommended -- and Firewire or USB2 generally works best. External makes it easy to transport to other studios when doing work elsewhere. Look for at least 350 GB storage capacity -- more if you can afford it.
Step 2: Max Out Your RAMIt's no secret that the more RAM you have, the better your computer runs. The difference between 512MB of RAM and 2 GB of RAM on a recording machine is staggering -- everything will run faster, you'll be able to run more recording plug-ins and effects, and you'll be able to work in a multi-track environment without issues. If you're running a PC, at least 1 GB is recommended; for Macs, especially the new i5 Macs, 4 GB minimum is the standard. And don't skimp on the quality of the RAM you buy; the higher quality chips do have a slight performance advantage over the cheap ones.
Step 3: On a PC? Shut Off Unnecessary ServicesMacintosh has long been the favorite of recording engineers because of it's underlying stability, especially the UNIX-like backbone. However, if you're stuck running Windows and don't want to convert to Mac, there's still hope!
If you must run an anti-virus software, choose a lightweight one that doesn't constantly run in the background. Also, disable all background and task bar services that aren't 100% necessary. Visual effects, the background image, system sounds, and other aesthetic options are resource hogs you can do without, too.
Step 4: On a Mac with OS X? Disable Dashboard & WidgetsOne of the coolest parts of Mac OS X is the Dashboard application and the associated Widgets. As much as it hurts to say this, Dashboard is a resource hog that you don't need active when recording. Sorry, Steve Jobs. Let's do some housecleaning to keep OS X running.
Drop into your Terminal application (it's in Utilities), and type the following: defaults write com.apple.dashboard mcx-disabled -boolean YES followed by killall Dock.
Your Widgets aren't lost forever; you can reactivate them in Terminal by typing defaults write com.apple.dashboard mcx-disabled -boolean NO along with the killall Dock command.