Your power supply should have an operational fan. You can try cleaning with compressed air to see if it will start but these do fail. Most are basically 80mm case fans with a different connector. If you are enterprizing, you can replace the fan yourself. If not, you replace the power supply. Your processor should have a fan as well but some used passive cooling (heat sink only relying on air flow within the case. Are you sure the precessor has no fan? Your celeron is not a power hog and should step back it's speed if it gets too hot. Some of these were mounted flat on the motherboard and some in were in riser cards (slot 1). The fan is not always apparent in slot 1 modules so you need to look closer. A celeron 700 with 320 megs of RAM is not going to burn up the dragway when loaded with XP Pro no matter what you do but you do need to address cooling issues.
I am running windows xp pro. version 5.1.2600 service pack 2. Total physical memory 320 mb. Not for sure where to find model # but did fine system model #nocppo12. processor intel celeron 700MHZ. I hope that is what you might need to help me. I only have 1 fan and it is behind where the power cord plugs into. I have noticed that my computer is real slow opening up anything and my computer is pretty hot. Have not heard the fan come on at all so took the case off, it was not dusty in the case but fan is not working. Should I take fan out and try to clean it on the inside or should I just try to buy another one. This computer is just used for home. Thank you for any help you can give me.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic