cant dispute that because i don't have a p4 kicking around to try it on ,but im sure it tried in the past on a pyx86 and it did not alow me to load win7 64bit onto it because it was not 64bit compatibleYes, but almost anything after Pentium 4 will run 64 bit. For the normal end user like me, a 64bit OS is highly recommended especially with 4GB of RAM and above.