I have to recommend against using MSConfig to disable parts of the Windows OS. Professionally, MSConfig is a cancer that should have been removed long ago. Using it covers up the symptoms but does not eliminate the problems.
You should use a good AntiMalware solution (like AVG -- disclaimer, I am a reseller, but for good reason,) and Windows Defender. Between the two, I have kept many a system clean, and cleaned up many a system.
Defrag your system, that will make a marked increase in performance, especially if critical system files are spread out across the drive. And I don't mean just core Windows stuff, I mean anything that loads at start up.
Remember that Windows XP loads just enough to get the Desktop up and loads other items in the background. This can cause a perceived loss in performance upon first boot, and also when first running programs. Once programs get loaded, XP caches important parts and subsequent runs are MUCH faster.
Check your Virtual Memory size. For whatever reason, I've seen a lot of XP loads that have static paging files set. They should be set for "System Managed," and if you have multiple drives, I recommend spreading it out across drives. You should have a paging file on your C: so XP can perform memory dumps when necessary, but you can also set one up on other partitions (non removable) to increase performance. To the end, you should also make sure you have plenty of extra space available on the drives used for paging file.
And newer hard drives will far outperform older drives. It's amazing what replacing an old Maxtor 20GB ATA133 drive with a newer 80GB ATA133 does for data transfer.
If you're using IDE, don't put your fast C: on a the same cable as a second slower drive, or non-DMA CD-ROM.
Clean up your Internet Explorer cache. This is one part of the system that is actively indexed, so the bigger it is the worse off you are.
HP printer drivers are the devil. They will often eat your performance. Try to use only the corporate editions of the drivers without all the extra fluff.
Use Windows Defender to find startup items and REMOVE them as necessary. QuickTime, RealPlayer, DivX Player, Word Perfect, et al have pre-loaders that are unnecessary if you use them infrequently. Other programs like Yahoo! Messenger, AIM, Windows Messenger also have options to load when Windows starts... start them manually when needed, and don't let them sit in the clock tray when you're done with them.
Also watch for special drivers and programs that communicate with other hardware. For instance, I have a Sony Ericsson phone that I synchronize with my laptop using the SE Phone Suite. After I sync, I have to kill "epmworker.exe" or else my system freezes every 10 seconds or so as the SE Phone Monitor checks Bluetooth for phones. I've {bleep}ed about this numerous times but it's never been fixed. Essentially, I have to reboot my laptop any time I want to sync my phone.
Use the latest drivers available for your hardware. A buggy video driver can cause all sorts of problems.
Also, run a diagnostic on your hard drive. A slow system has often proved to be the result of a hard drive having to do extensive error recovery (some drives can take up to a minute to correct a bad sector.) Windows will sometimes log this problem in the Event Log. Which, BTW, can also be a great resource in finding problems... but not always, unfortunately.
Gotta run.
