So i was thinking about getting WIndows 7

My hardware is pretty new, (bought this last year)

Operating System: Windows 7 Professional 64-bit (6.1, Build 7600) (7600.win7_gdr.100226-1909)
Language: English (Regional Setting: English)
System Manufacturer: Hewlett-Packard
System Model: HP Pavilion dv7 Notebook PC
BIOS: Default System BIOS
Processor: Intel® Core™2 Duo CPU T6400 @ 2.00GHz (2 CPUs), ~2.0GHz
Memory: 4096MB RAM
Available OS Memory: 4062MB RAM
Page File: 1757MB used, 6366MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
DX Setup Parameters: Not found
User DPI Setting: Using System DPI
System DPI Setting: 96 DPI (100 percent)
DWM DPI Scaling: Disabled
DxDiag Version: 6.01.7600.16385 32bit Unicode

and I'm not the only one with this issue.
If you were to google firefox memory leak windows 7 64 bit, you're going to see tons of complaints from different people.
http://www.google.ca/#hl=en&source=hp&q=...9804149ebd
Same goes for the other 2:
http://www.google.ca/#hl=en&q=google+chr...9804149ebd
http://www.google.ca/#hl=en&q=MSN+freeze...9804149ebd

And finally get 64 bit if ONLY if your computer have over 4GB of memory, 32 bits can handle 4GB of memory.
(Also 64bits computers is slower by a small fraction of a millisecond because the memory address doubled, meaning it takes twice the amount of time for the CPU to process the memory address)

And I think you can only get 32 bit anyways, cause I read somewhere mac doesn't have 64 bit OS.