I got the same problem. I've had it for two years and ignored it until now because it's become necessary to repair it finally. Go here click on "Systems" and find the correct listing for your 4300. Then when you are taken to the User's Guide for your system, scroll down to the Repair and Replacement section (in your case I think it is called "Adding Parts") and begin reading about replacement of Power Supply, Heat Sink, and microprocessor.

I suggest you check this fan or as technically called Power Supply. There might be a possible problem with it, but if it keeps getting louder, maybe its a sign that you may need a new one. Search at TigerDirect http://www.tigerdirect.com and NECX Direct http://www.necxdirect.com to check for power supply that is suitable for your system and motherboard (check possible Dell manuals for the correct configuration of power supply for your system). Or even check Dell's Tech Support if possible. Hope this helps and good luck

Ginger "Angelique Valeriano"
Dell Inspiron 7500
6 GB (Primary)
25 GB (Secondary)
Toshiba CD\DVD-ROM Combo
288 MB RAM
Rage Mobility (Video)

Fans are a necessary evil with hot CPUs. I have 4 case fans, cpu fan, chipset fan, power supply fan. You should here mine!! They aren't bad but you know their there, which is comforting. My CPU runs at a cool 79 degrees F. And MB runs 78 degrees!

Pentium 4 1.9 Gig / 478 pin 400Mhz FSB
Shuttle Motherboard
Via chipset P4x266 VT8233 DDRam Support
Windows XP (home edition)
DDRam 768 M
WD 80 gig HD ATA 100
Gainward GF3 Powerpack Golden Sample
LiteOn 24x10x40 CD-RW
Pinacle Firewire Card
Santa Cruz Sound Card (4127 beta drivers)
Linksys Lan Card
Dell 991 Monitor
Microtek 3700 Scanner
HP 1100 Printer
Logitech Pro 3000 web cam