|Its unnecessary features that are not typically used by users, or just generally use more system resources than necessary, while offering little or no benefit to its users|
on windows XP you can use start>run> type msconfig and go to "start up" tab disable everything that you dont NEED to start the pc. Most Windows files can be left enabled, aswell as any Virus/Firewall software you may have.
Stuff like printer software, any game clients, any messenger service (MSN, Yahoo, AIM) and adobe crap can be disabled.
And might be a good idea to look at add/remove programs and go ahead and remove anything you dont use.
Also might look into memory upgrades, as suggested above.
Intel P4 640 w/HT 3.20GHz
2GB DDR2-SDRAM PC2-6400
Nvidia GeForce 9600GT 256-bit, 512MB GDDR3
23" LG Flatron