Bootcamp on Lion

Hi - I would really appreciate some advice.

About a year ago I moved from a PC running Vista to a MacPro, now running Lion.

I'd like to set up a Bootcamp partition (to run some old PC programs) and understand that Lion requires Windows 7.

Ordinarily I would just buy an upgrade, but the upgrade process will look for an earlier version of Windows - which of, course, it won't find as Lion won't accept Vista...

Am I forced into buying a full version of Windows 7, or will is there a way that I can go for the (cheaper) upgrade option?

Thanks very much

Julian

You can buy Win 7 Home Premium for around £70 ($108) for an OEM version from Amazon instead of going for the more expensive Retail versions.