Here's my system specs as generated by the blizzard beta profile settings app:

OPERATING SYSTEM:
MacOS 10.7.3
CPU TYPE:
Intel® Core™2 Duo CPU P8600 @ 2.40GHz
CPU SPEED:
2.42 GHz
SYSTEM MEMORY:
4 GB
VIDEO CARD MODEL:
NVIDIA GeForce 320M
VIDEO CARD MEMORY:
256 MB
VIDEO CARD DRIVER:
-
DESKTOP RESOLUTION:
1280x800
HARD DISK SIZE:
232.09 GB
HARD DISK FREE SPACE:
25.16 GB (11%)
DOWNLOAD SPEED:
2.12 MB/s (17.8 mbps)

I'm trying to determine what computer to use, macbook pro or my older windows desktop. here are the desktop specs:

Case ( Coolermaster HAF 932 Full-Tower Gaming Case )
Power Supply ( 800 Watt )
Processor ( Intel Core 2 Quad Processor Q6600 (4x 2.4GHz/8MB L2 Cache/1066FSB) )
Motherboard ( [SLI] MSI P7N SLI-FI Nvidia nForce 750i SLI Chipset w/7.1 Sound, Gb LAN, S-ATA Raid, USB 2.0, IEEE-1394, Three PCI-E MB )
Memory ( 4 GB [2 GB X2] DDR2-800 PC6400 Memory Module )
Video Card ( eVGA NVIDIA GeForce 8800GT 512MB w/DVI + TV Out Video )
Hard Drive ( 320 GB HARD DRIVE [Serial-ATA-II, 3Gb, 7200 RPM, 16M Cache] )
CD/DVD Drive ( LG 20X Dual Format/Double Layer DVD±R/±RW + CD-R/RW Drive )
Sound Card ( 3D Surround Sound Onboard )
Network Card ( Onboard LAN Network (Gb or 10/100) )
Flash Media Reader/Writer ( 12-In-1 Internal Flash Media Card Reader/Writer )
Operation System ( Microsoft Windows Vista Home Premium 64-bit )

I've been pretty unhappy with my desktop machine. it seems to be very unstable and just overal slower then i want. i just reloaded the system with a clean install of everything and still am not happy.

any suggestions? are there any improvements i could buy for the desktop which wont cost over $500? i was thinking a new motherboard and gpu, but not sure if my CPU will still fit in a new motherboard