For any new computer purchase, ensure that your new PC is at least "Vista Capable," although we recommend "Vista Premium Ready."

Vista Capable

• A modern processor (at least 800 MHz)
• 512 MB of system memory
• A graphics processor that is DirectX 9 capable

Vista Premium Ready

• 1 GHz processor
• 1 GB of system memory
• 40 GB hard drive
• DVD drive
• A graphics processor with 128MB of memory

Learn more after the jump

http://www.microsoft.com/windowsvista/default.aspx