¹ With the exception of Windows 7, minimum RAM specifications in this table are higher than Microsoft's original unrealistically low minimum requirements. Computers configured according to this table will run acceptably for most users.

² Sixty-four (64) bit versions of Windows XP and Windows Vista can effectively address up to 128 GB RAM.

³ Windows Vista 64-bit Basic Edition supports up to 8 GB RAM. All other 64-bit versions of Windows Vista support up to 128 GB RAM.

⁴ Windows 7 and Windows Vista 32-bit editions cannot access more than 3.50 GB system RAM. System Properties may show 4 GB or more.

⁵ Windows 2000 Professional extended support ends July 13, 2010.

Windows Vista 64-bit software is included only with Windows Vista Ultimate Edition retail package. Other 64-bit versions may be ordered from Microsoft or may be supplied as an OEM product from Dell, Gateway, etc.

Windows 7 64-bit and 32-bit software is included with all retail versions of Windows 7. OEM versions from Dell, Gateway, etc. will be either 32-bit or 64-bit depending upon pre-installation. 64-bit installations are now commonplace with retail computers.

Windows 7 maximum addressable RAM is version dependent:

32-bit:
Windows 7 Starter - 2 GB
All other Windows 7 32-bit versions - 4 GB (3.5 GB max addressable)
64-bit:
Windows 7 Home Premium - 16 GB
Windows 7 Professional - 192 GB
Windows 7 Ultimate - 192 GB

Current hardware limits personal computers to 24 GB RAM. This limit will increase with advances in technology.

Reportedly, Windows 7 will be the last operating system released by Microsoft in both 32-bit and 64-bit versions. Future versions of Windows will be 64-bit and/or 128-bit.

¹ Windows Vista Service Pack 1 is prerequisite for Windows Vista Service Pack 2.

Reviewed 2/08/2010