How much RAM does your system have? Has it always had the same amount of RAM, and how many programs have you added over the years?
I usually find that adding more RAM solves most problems, as most mainboards will usually hold more RAM than is fitted (unless sold with the 4 x 1024 MB maximum for 2000/XP) as they are usually sold with the - minimum - amount of RAM necessary to run the software that they come packaged with.
So when buying a new computer - always - ask to have additional RAM fitted if this option is open to you and you can afford to do so.
512 MB is a minimum for 2000/XP if you plan on doing - any - multitasking.
Many newer computers are fitted with 1024 MB as standard, simply to allow people to play 'high-end' games, but Professional users - often - have 1024 MB RAM, or more, fitted for large Office and Imaging programs used in multi-tasking, especially when an internet Browser and an Email client are running at the same time, plus scheduled anti-virus or other scanners and where automatic defragmenting programs are allowed to start up automatically.
Some defragmenting programs will operate 'seamlessly' so that you don't notice, only working when you stop using the computer for a few seconds or the processor is idling but many scanners do not operate seamlessly and need to be allowed for.
