changing too many at once is about the only thing which triggers this.
you can upgrade ram whenever you want, it's jsut that 32-bit wont recognize over 4gb.

sorry if you dont believe this, but i've been reading about htis and using it since day 1.

and i've used oems (generic, not an actual brand name oem) and rtms and never had to re-install the key.

using computers sonce '78
using windows since 3.11 including vista &7 since beta1
repairing, rebuilding, building, selling and support since '92

View the original article here