Vista registry edits ineffective

I have an Acer Aspire 6920 with Windows Vista Home Premium and I made a couple of registry edits. The edits were ineffective. One of the edits I did was this http://support.microsoft.com/kb/930526. I tried the same on another vista machine and they worked fine.

Why don’t these work, is there a security setting that I am messing or override of some sort? Is the Acer pre-installed software hindering my edits?

Thanks in advance for any help.