>>I have disks for W7 Enterprise and W7 Ultimate so it seems there's more than one version.
>>But I haven't used them so have no advice on installing over XP.......
>
>Ok, what I have is Windows 7 Ultimate.
>
>I need to make sure I will be able to keep all the servers I have installed on it such as IIS, SQL Server and so on.

Sounds risky to me. I'd make a ghost copy of the drive before trying it.....