Whirring Noise

[Majicman1944]

I have read the thread on the possibility of this issue being a dirty fan. I have cleaned the whole fan area & all other areas that I am able to do so in. I have also tightened any screws which may have been loose in conjunction with this issue. The whirring sound is not always present. Many times it will take 15 to 20 minutes for it to begin. As a test, I have laid the unit on it's side when the whirring noise occurs. When I do this, the noise ceases. This is not my primary computer but I use it as a backup to my windows 7. It is a Dell, E521 with the following:

AMD Athlon Processor- 3500 2.2gh
958 MB Ram
32 Bit Operating System
Windows Vista

I am hoping someone can give me a definitive answer as to whether this is definitely a fan issue or could be something else. Any help will be greatly appreciated.

[Allan]

Run the system with the cover off and see if you can identify the location of the noise. Be careful not to touch anything inside while it is plugged in to power.

[Quantos]

The whirring sound is not always present. Many times it will take 15 to 20 minutes for it to begin. As a test, I have laid the unit on it's side when the whirring noise occurs. When I do this, the noise ceases.

Is there a cable near a fan?  It may be coming into contact with the fan, and when you move the computer it then breaks contact. 
It could also be a fan that's in need of replacing.