I cannot get the 64 bit version to install. I gets so far and then at a reboot I get the "hardware or software problem screen that says it encountered a problem and shut down so as to not harm the computer. The 32 bit installs fine.
This is a new machine and these are the components.

ASUS M2N-SLI Deluxe AM2 NVIDIA nForce 570 SLI MCP ATX AMD Motherboard

AMD Athlon 64 X2 5000+ Brisbane 2.6GHz 2 x 512KB L2 Cache Socket AM2 65W Dual-Core Black Edition Processor

COOLER MASTER Real Power Pro RS-750-ACAA-A1 ATX12V / EPS12V 750W Power Supply 115/ 230 V Nemko, TUV, cUL, CE, BSMI, FCC, CCC

HIS Hightech H260XTF512DDN-R Radeon HD 2600XT 512MB 128-bit GDDR3 PCI Express x16 CrossFire Supported Video Card

ARCTIC COOLING Freezer 64 Pro 92mm CPU Cooler

CORSAIR XMS2 2GB (4 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory

SIGMA La Vie LBYWBP Leather Black SECC Steel ATX Mid Tower Computer Case 500W Power Supply

Microsoft Windows Vista Ultimate DVD

remove all but 1gig of ram and try to install Vista 64 this is a common problem.

I disagree, his RAM at 4GB's is not the problem, checking your BOIS for proper config. for the 32bit to 64bit upgrade might just do the trick!!