An invaluable tool for identifying rogue processes on your PC is the Windows Task Manager.
Pressing Ctrl + Alt + Delete simultaneously brings up the Windows Security dialog box, which presents you with six options: Lock Computer, Log Off, Shut Down, Change Password, Task Manager and Cancel. Clicking on Task Manager will open a list of all the applications you have open.
Look through the applications list for any programs that have stopped responding. Close them accordingly by highlighting each one and clicking End Task.
If that doesn't speed things up, click on the Processes tab to see the complete list of programs running on your PC. The third column titled CPU indicates the percentage of the processor each process is currently using. Windows updates the list frequently so you might notice the numbers change automatically.
Click on the CPU column heading to sort the list into ascending order. Click it again to re-sort the list so processes utilising the CPU the most (indicated by higher numbers) are at the top. Ignoring System Idle Process, identify any processes with high CPU values. If you're unsure if it needs to be running, type the process name into Google to find its purpose.
At this point, it is a good idea to save any open documents. To close a problematic program, highlight it in the Windows Task Manager and click End Process. Click Yes on the warning pop-up that follows.
If nothing looks out of the ordinary in CPU usage, check to see if any processes are hogging the memory by clicking on the Mem Usage column. Similarly, highlight any runaway processes and click End Process to free up some memory.
For further performance tips, check out CNET.com.au's do-it-yourself guide to speeding up Windows XP. Malicious software can also PCs to slow down, read our spyware FAQ to find out how to eliminate spyware and stay protected.