Update to Win 7 from Vista Hme Premium

Intel DP55WB mobo with Intel i5 750 CPU.
I tried to upgrade from Vista Hme Premium to Win 7 Pro using Win 7 Pro Upgrade disc; received an error msg saying that upgrade procedure was not allowed !!

I fell back to upgrading using a Win 7 Hme Premium disc.
Because the Win 7 Pro upgrade disc cost more than the Win 7 Hme Prem upgrade disc, I do not understand MS's refusal to allow this upgrade to a more costly product.

I know I may pay an additional fee to upgrade from Win 7 Hme Prem to Win 7 Pro;
and/or use the Win 7 Pro upgrade disc to achieve the same step-up, but that burns two Win 7 upgrade Keys to upgrade one machine !!

Am I missing something? If someone can, will you please explain the Why of this.
Also, are there alternatives?

Suggestions welcome.
Tks

Unfortunately the upgrade path is from Business>Pro since Pro is seen as the successor to Business.

Try Premium for awhile as many find they have all they need in it. Unless you need BitLocker, or Virtualizing, or initiating Remote Desktop (which is better done via Team Viewer) then Premium may be all you need.

Pebbly provides the ultimate solution: Do the Pro clean install which is superior anyway! When you boot the Pro installer, it will see any OS on the HD to allow use of Upgrade key, even if you then use Custom>Drive Options to delete, repartition and format before install.

However now that you're running 7 Premium if you want to change to Professional there is a popular workaround to change versions within Win7 that works very well and will reset your activation to insert the Pro key when finished. Let me know if you need it.