Computer fans making loud whirring noises ?

I need help and to know what to do now.

I keep hearing that the computer fans could be dying and that would then kill the computer as well.

I dont know what happened I had the computer on all the time but the last few days when I started shutting it down and booting it up the next morning it now makes this horrible sound in both fans in the inside of the tower.

It sounds like they are pushing too hard or going into overdrive or even overheating but I dont know what exactly it is precisely.

I need help this computer cost enough money as it is I dont want it to die on me weve had it since 2009.

Please help.

If it helps :

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft® Windows Vista™ Home Premium, Service Pack 2, 64 bit
Processor: AMD Phenom(tm) 8450e Triple-Core Processor, AMD64 Family 16 Model 2 Stepping 3
Processor Count: 3
RAM: 7934 Mb
Graphics Card: ATI Radeon HD 3200 Graphics, 256 Mb
Hard Drives: C: Total - 476937 MB, Free - 210638 MB;
Motherboard: Dell Inc., 0F896N
Antivirus: Microsoft Security Essentials, Updated and Enabled