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 the Recommended RAM column will run acceptably for most users. Computers with Minimum RAM may at times exhibit sluggish response.

² Sixty-four (64) bit versions of Windows Vista can effectively address up to 128 GB RAM. Exception: Windows Vista 64-bit Basic Edition supports up to 8 GB RAM. See Windows 7 Notes below for information about Windows 7 addressable RAM.

³ Windows 7 and Windows Vista 32-bit editions and Windows XP cannot access more than 3.50 GB system RAM. Depending upon hardware configuration, Windows XP may show less than 3 GB available RAM while Windows Vista and Windows 7 may show 4 GB or more in System Properties.

⁴ Windows 7 Professional/Ultimate requires additional RAM for XP Mode. Add one gigabyte to the listed minimum RAM if planning to install XP Mode.

⁵ Windows XP SP3 minimum available RAM recently reviewed. Desktop computers for the most part will run fairly well with 512 MB after several minutes. Some older PCs (such as my 2005 vintage Toshiba) should have at least 704 MB RAM available to the operating system.

Recent updates plus Microsoft Update utilizing more RAM shortly after OS loading have seriously impacted the usability of the operating system during startup. Furthermore, most security and printing suites are resource intensive and can cause sluggish response at startup and during normal operation. Additional RAM can alleviate these issues.

⁶ Windows XP will accept 4 GB RAM. Typically only 2.9 to 3.5 GB is accessible.

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 Notes

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 prevalent among 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

Reportedly, Windows 7 is to be the final 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.

² Windows XP Service Pack 1a (SP1a) or SP2 is prerequisite for Windows XP Service Pack 3.

Revised 1/18/2012