Most of us use Windows XP and may be doing so for many more years. I've had my problems with XP slowing to a crawl and have found a few services that can be turned off that have made a big difference in performance for me. You can turn off these services from Administrative Tools / Services. Right click then properties to set to "disable" or "manual". Personally, I use Ultimate Troubleshooter by Answers That Work to make such modifications. Here are services that almost everyone doesn't need. PROBLEM: Computer hangs and runs erratic. Some taskbar icons don't load. FIX: Turn the following services to "disable": srservice upnphost ssdpsrv Upnp devices cisvc Indexing Service messenger network function ersvc Error Reporting Windows Restore (disable through the controll panel. You should be doing daily backups to an external usb drive.) Flush the DNS and renew the IPs: At Start>Run, type in cmd and press Enter. At the comand prompt, type in ipconfig /flushdns and press Enter. At the command prompt again, type in 'ipconfig /renew and press Enter Reboot after making the changes. You can always turn any of these back on at any time you wish by reversing the process. I think you'll find a much faster computer by turning all this junk off.
You can also speed up XP by installing Intel X-25M G2 SSD + 4G RAM. Recommended tweaks include turning off drive indexing, system restore, prefetch and page file.
A few years ago I used to spend too much time with this service list, but not any more. 1. Too time consuming 2. If I got each service selected as per list AND it didn't cause any problems with any apps, I only saved about 10 MB of RAM (or less) and a few seconds (maybe not even a few) at startup. Extra services which go unused basically just take up a bit of RAM space without impacting function... or so it seems on my rigs. 3. If I had a problem with an app, it was sometimes a pain to go back over the services to see which one was causing the problem. 4. I perceived no speed-up in operation with the trimmed list. So, I no longer bother. FWIW...
That's generally true. However, I've found turning off the first three services I mention above made a noticable difference in my computer performance. It seems that there is a point at which you have so many things loaded in Windows that these three really start to effect performance. One other thing I've had a performance problem with is McAffe Antivirus. Several years ago I noticed a performance drop with McAffe turned on so I switched to CA and have had no problem since.
That's because most antivirus programs themselves are viruses, starving your computer of precious CPU cycles.