BleepingComputer.com: setting privileges from install disk command prompt

My week-old Dell laptop running Vista Home Premium 64 bit has suddenly presented me with the not unfamiliar boot-to-blank-screen-with-moveable-cursor syndrome even when F8-ing to Safe Mode with Command Prompt.

The install disk repair option tells me there's nothing wrong with Vista, but I tried a System Restore just in case it helped, but it didn't. Before I trash the whole carefully set up system and use the recovery partition, I thought I'd try the command prompt from the install disk to get msconfig to turn off everything.

Problem is, when I navigate from X:\ to C:\Windows\System32\ and try to run msconfig.exe, I'm told I don't have sufficient privileges to do so. How do I establish my identity as Administrator in order to run msconfig? Don't forget I have to do this AFTER invoking the command prompt, because I'm running cmd.exe from the installation disk.

I have to confess I've already posted a similar question on the Microsoft Community forum, but so far I've had no replies...