I would have to RECOMMEND only DL and install from a Original Edition of M$ iso... you can remove the ei.cfg from the iso... then you can burn and chose what Edition you want to install.... you get 30 days - then you have 3 rearms to continue for upto 120 days total....
prior to that I used 1 of 2 different Activator programs - every one has passed everything I have tested thru M$ Official Beta Tester, including SP1 B1.
1. I use Orbit30 ULoader 8.0 and activate via SCRIPT... not the auto GUI.... Script included so you can change to your Manufacture and Edition for Proper Certificate and KEY.
(most are included with the program...)
2. There is a NEW Activator that has (currently passed all tests -) called ODIN by Secr9tos v.1.3.7
I can-Do recommend #1 or #2
&
3. The newest version of Chew7 v1.0 build 0.6.7.3 by Anemeros ( very hi reviews) tho I currently have not TESTED my self...
Both #1 and #2 have the ability to Re-Activate and REMOVE many of the PRE-ACTIVATED stuff which does not pass M$ -Pirate Catchers.