If your PC has been running extremely slow lately, frequently freezing up, or crashing, then you may need to optimize Windows XP.
More often than not, the vast majority of problems that cause Windows XP to become so buggy, can be fixed by implementing one or more of the following 4 solutions below:

1. Run anti-virus software on your PC.
   If you're already running it in the background on your PC, run a full, comprehensive scan, at least once, to make sure that nothing has been missed.
   Also make sure that you have downloaded the latest virus definitions so that your anti-virus program is up-to-date.
   
2. Run anti-spyware software on your PC.
   Spyware is similar to viruses, in that both viruses and spyware make their way to your PC by means of stealth.
   The main difference is that viruses are intent upon destroying your system or your data.
   Spyware is intent upon spying on you, stealing information from you, and defrauding you.
   
3. Run disk defragmentation software on your PC.
   Over time, as your computer's hard disk gets full, your PC will attempt to store new data in whatever available physical location it can find on the disk and this data may not necessarily be in a contiguous locations.
   In other words, the data is scattered.
   This makes your PC's hard disk work harder to read information from and write information to your hard disk.
   This will slow your PC down.
   Defragmentation reshuffles all of the data on your hard disk
4. Repair your Windows registry.
   The Windows registry is the master database that Windows uses to store all of the information about every piece of hardware or software that has ever been installed on your machine.
   Over time, the registry can grow very large.
   Errors due to outdated and invalid links can creep up.
   This makes searches against the registry inefficient and error-prone.
   Registry errors are one of the leading causes of Windows instability and slow response.
   

If you can implement one or more of the 4 solutions recommended above, you can resolve the vast majority of problems that cause Windows to become sluggish, buggy, unstable, and unreliable.