* Make sure all external programs are closed (especially any download programs!).
* Check your computer for adware/spyware/malware with...
SPYBOT: Search & Destroy (FREE)
Microsoft's Anti-Spyware Beta (FREE)
Ad-Aware (FREE - But PRO Version Is Best) would be a good idea too.

Another thing, it wouldn't hurt to defragment your hard drive(s). You can use the default windows program for this, but I recommend a program called Diskeeper (Faster & Does a better job)

Aside from that, make sure you have the latest updates for things.

MICROSOFT UPDATE ~ http://update.microsoft.com
ATI Graphics Drivers ~ http://www.ati.com/support/driver.html
NVidia Graphics Drivers ~ http://www.nvidia.com/content/drivers/drivers.asp

Oh and, just a tip; Automatic updates don't get ALL updates PLUS having that on can cause lag in-game if it decides to download while you're playing. I recommend turning it off.

ALSO

If you think STEAM is a problem; Open up the games list and right click any non-3rd party game (Ex. Half-Life, Half-Life 2, Counter-Strike, Opposing Force) and click PROPERTIES and change them to not keep the game up to date. Then the game will only update next time you run it.



THE FOLLOWING WILL WORK FOR NORMAL CLIENTS AND SERVERS

At the System Properties Window (control panel -> system)

1. Get rid of system restore (turn it off) (system restore option)

2. Uncheck the automatic updates (Automatic option)

3. In the advanced setting go for performance settings.Adjust it for best performance.

4. XP Pro ONLY - Open "run" window, and run "gpedit.msc". follow this tree, computer configuration, administrative templates,network, QoS packet scheduler, at right window, right click on "Limit reservable bandwidth" and get properties, in the new window, make this enabled, and in the bandwidth limit (%) part enter 0 (i mean zero), apply and exit.

5. Go to this page --> Black Viper's Win Registry Page *CURRENTLY DOWN* Go HERE, in this
page you will find some registry files, "safeproallstart", "safehomeallstart",
"gameingproallstart", these files are really great, they will disable many of windows xp services that are useless and can occupy memory and cpu usage.
I recommend "safe" settings because they do not harm anything, besides try to learn everything on that page, do not disable any
service from msconfig, thanks to this cool guy.

6. Get TweakXP from TweakXP.com, this is the most coolest application that
I have ever seen for tweaking WinXP, configure it due to your needs, and do not forget the hardware part, it can help alot.

7. If you have Service Pack 1 installed, and you use a hlds with windows media player or flash player (for high HLDS fps) use this tweak for decreasing cpu usage that mediaplayer eating,
run regedit, go and remove this key: HKEY_LOCAL_MACHINE\SOFTWARE\Classes
\CLSID\{87D62D94-71B3-4b9a-9489-5FE6850DC73E}\InProcServer32"

8. If you use a standalone server for HLDS (not for any other usage), try to disable any sound system on your computer.

9. Disable any kinds of indexing service on your hard disk partitions.

10. Disable any kinds of power managment for your hard disks.

11. Always use the lastest drivers for your mobos, latest Bios upgrade and so on. Most of the times you can download these things from your mobo's manufacturer.

12. Don't forget most of smooth servers are using cpus with a large amount of L2 cache and front side bus, and a great amount of RAM!!!

13. Run msconfig and at the "startup" option try to uncheck every unneeded application or ...

14. Try to defrag your hard disk every 2 weeks, this helps alot for having better H.D.D performance.

15. Try to have a great cooling system for your server.