"I have read sites that say you can do some simple editing and windows will upgrade the beta to RC1."
True but not rcommended, however you still need the W7 RC program disk for the upgrade, the workaround is only to ENABLE an upgrade, it does not in itself upgrade the system to the RC.
In Australia we had a magazine released with a Windows 7 ISO on it, I can't remember which one it was, I already had W7, so didn't bother getting it.
Have a look and see if you can find one in your local shop to see if you can find one with it on the cover dvd, or maybe someone you know can make you one.
You can still get a key from Microsoft if you have a copy of W7 RC.
OK I found the issue with Windows 7, it was on the August PC Authority issue.
I don't know if you can get it where you are.