|"But the thing is I know Dells are usually set up to not work if you dont have a certain part, for example the heatsink or heatsink tray".|
You are correct that your Dell needs certain replacement parts in order to work.
The key replacement part IS the motherboard. Without a close match to the original one your copy of WinXP will refuse to run at all.
A celeron 2.6 is not worth enough to build a computer around it. The link below is an example of what it may be worth.
Dell motherboards will be expensive.
As jam stated above you need to try and determine what part, if any, is defective.
Post details of what is happening.