CPU Upgrade

VT-x  Requires BIOS, CHIPSET, and PROCESSOR updates. I do not know if BIOS A05 has this feature. Nor do I know if the 5150 supports this. There are 2 Dimension 5150's the 5150c doesn't support pentium D 960.  Earlier Smithfield processors DO NOT SUPPORT VT-x

http://downloads.dell.com/bios/D5150A05.EXE

E510       D805 or D925

The 0HJ054 motherboard is the best one for upgrading the CPU.

http://ark.intel.com/products/27522/Intel-Pentium-D-Processor-960-4M-Cache-3_60-GHz-800-MHz-FSB

Also Keep in mind that VT-x is supported but VT-d is not.

This system is NOT suitable as a vmware ESX server.

It will not show up at all if the CPU doesn't support that feature.  It does work with Optiplex 620 and Higher TOWER with 305W power supply,

Very few of the 2005 penitum 4 family support this or ever will support this.

Pentium D 960  SL9AP   SL9K7

95 Watt (775_VR_CONFIG_05A)
130 Watt (775_VR_CONFIG_05B) 

Both versions of Pentium D 960 (SL9K7 - D0 - 95W) or (SL9AP - C1 - 130W) on a GX620 will need DELL Performance Heatsink J9761 and BIOS A11. I also recommend Arctic Silver 5 (Thermal Paste).

Thanks for the reply. It seems like I need to change a lot of things that I am not capable to do so.

Your information though it will be taken into consideration whenever possible.