G'Day, long time no post anyhooow

- I have a brand new box that I won't be upgrading for a while hardware wise.
- It has a retail version of Windows XP Pro on it.
- I want to upgrade it to Vista Ultimate and don't want to reformat and reinstall.

So am I right in saying that if I get a Vista Ultimate OEM that would be the cheapest way to get to Vista? And that there are no issues with using the OEM to upgrade the XP Pro install?