It will be compatible... just enough to make you wish to upgrade the rest. :)

>I wonder how comapatible it will be with existing software/hardware? Will it run all the old stuff still? I had to do hardware upgrades for XP, but it handled older software well.
>
>
>>http://www.pcworld.com/news/article/0,aid,121914,00.asp
>>
>>http://www.microsoft.com/windowsvista/default.mspx