There are several excellent software components you can acquire to make your installation of Windows XP work faster. Your computer is likely capable of much higher performance than Microsoft sells you. Why this is so, I do not know.
Hardware - Software competition and Eaves [boring]
It is possible to increase computer performance by perhaps 30-50% by changing standard tweaks in hardware and even in programs like Mozilla to make your computer and network run faster. The average consumer simply believes that if the computer is too slow it either has a virus on it or it has gotten old and you need a new one. Have software companies exploited this decaying of performance to spur new computers being bought? The same style of workmanship has shown up in automobiles from time to time and more recently since the and 1970's.
I have also noticed a considerable amount of 'built-in' surveillance port options that cannot be unchecked. Automatic wireless cards, printers that always keep tabs on what they print, autonomous network activity. Spyware, Adware, and the NSA's law mechanisms and mandatory backdoors to all registered software. This should be outed like financial monitoring.
Tweaks [juicy meat]
Beyond this, some of the better ways to recapture strolling performance is through software. TUNE XP 1.5 from Driverheaven [DH] at Majorgeeks.com [use the TX download site] can produce several fixes.
UDMA-66 is a good starter tweak. It is accessible in the BIOS settings [which you can get to by tapping DEL at startup]. The UDMA cable runs from the motherboard to some device in your computer, and the 33/66 is the number of cables it contains. Since 1998 or so computers have used 66 or 100 cable UDMA cords. Windows automtically assumes you're using UDMA-33 even in 2006. Strange flaw. Changing this in the BIOS or TuneXP will increase the speed at which your computer talks to itself. =faster.
RAM latency ratings substantially improve RAM performance. Normal RAM latency for most models is 3T CPU cycles. That is RAM just plain *waiting* to do its duty. Most modern RAM can function at 2T cycles of waiting. You can find this also in the BIOS, and it should be under DRAM or SDRAM or DDR latency. Check it to "2" and your RAM will become, logically, 3/2 as effective. Or at least, one of the performance bottlenecks will be widened by that amount.
There is a DNS cache size, and I/O page lock limit, and there are settings of virtual RAM available for various functions that can each be adjusted upwards just by clicking. TUNE XP will get the DNS and I/O, and the pay program Advanced System Optimizer will get the other RAM setting.
Mozilla is a fine surfboard but it is limited to only one data request at a time. To about:config in the address line. There will be way down the list an http.networking.proxy.pipelining and another one w/o proxy a few lines down. they're booleans set to false. there's also a 'maxrequest' one set to 4. Set it to 30 and make the pipelines true by toggling them. then right click -> new -> integer and type in 'nglayout.initialpaint.delay' and set it to '0'. This will tell mozilla to wait 0 time bits before acting on info it receives. Bonus. It cuts out all the slack.
You can also play with overclocking your processor or video card, but if you do be sure to read everything everyone says about it first and try opening up your tower's airways in a safe manner. Maybe add an outside cooling fan. That's pretty chilly. Always remember to attack the bottlenecks. Changing your system from a 3Ghz chip to a 7Ghz chip won't help at all if you've only got 128Mb of RAM.
In the same way doubling your wealth won't help at all if there are still starving people in Africa.