Change the processer

According to it's manual these are your processor options:

version 1.0
10
Dell™ optiplex™ 755 technical guiDe
10
procEssor
Global Standard Products (GSP) are a subset of Dell’s relationship products that are managed for availability and synchronized
transitions on a worldwide basis. They ensure the same platform is available for purchase globally. This allows customers to reduce
the number of configurations managed on a worldwide basis, thereby reducing their costs. They also enable companies to implement
global IT standards by locking in specific product configurations worldwide. The following GSP processors identified below will be made
available to Dell customers.
Processor numbers are not a measure of performance.
processor (speeD
, cache, fsb)
mt
Dt
sff
usff
Intel
®
Core
™
2 Quad with Intel VT, Enhanced Intel SpeedStep Technology, Intel 64 and Execute Disable Bit
Intel Core 2 Quad Q6700 Processor (2.66GHz, 8MB L2 cache, 1066MHz FSB, VT)
✓
✓
✓
Intel Core 2 Quad Q6600 Processor (2.4GHz, 8MB L2 cache, 1066MHz FSB, VT)
✓
✓
✓
Intel
®
Core 2 Duo with Intel vPro Technology, Intel VT, Intel TXT, Enhanced Intel SpeedStep Technology, Intel 64 and Execute Disable Bit
Intel Core 2 Duo E6850 Processor (3.0GHz, 4MB L2 cache, 1333MHz FSB, vPro, VT)
X-GSP
X-GSP
X-GSP
X-GSP
Intel Core 2 Duo E6750 Processor (2.66GHz, 4MB L2 cache, 1333MHz FSB, vPro, VT)
X-GSP
X-GSP
X-GSP
X-GSP
Intel Core 2 Duo E6550 Processor (2.33GHz, 4MB L2 cache, 1333MHz FSB, vPro, VT)
X-GSP
X-GSP
X-GSP
X-GSP
Intel
®
Core 2 Duo with Enhanced Intel SpeedStep Technology, Intel 6.4 and Execute Disable Bit
Intel Core 2 Duo E4600 Processor (2.4GHz, 2MB L2 cache, 800MHz FSB)
✓
✓
✓
✓
Intel Core 2 Duo E4500 Processor (2.2GHz, 2MB L2 cache, 800MHz FSB)
✓
✓
✓
✓
Intel Core 2 Duo E4400 Processor (2.0GHz, 2MB L2 cache, 800MHz FSB)
✓
✓
✓
✓
Intel Core 2 Duo E2180 Processor (2.0GHz, 1MB L2 cache, 800MHz FSB)
✓
✓
✓
✓
Intel Core 2 Duo E2160 Processor (1.8GHz, 1MB L2 cache, 800MHz FSB)
✓
✓
✓
✓
Intel Core 2 Duo E2140 Processor (1.6GHz, 1MB L2 cache, 800MHz FSB)
✓
✓
✓
✓
Intel
®
Celeron with Execute Disable Bit
Intel Celeron 440 Processor (2.0GHz, 512K L2 cache, 800MHz FSB)
✓
✓
✓
✓
Intel Celeron 430 Processor (2.0GHz, 512K L2 cache, 800MHz FSB)
✓
✓
✓
✓