Rootkit Revealer is failing to run, why? [duplicate]

Solution 1:

Rootkit Revealer does not support and does not run on 64-bit Operating Systems. The fact that Rootkit Revealer fails to run on a windows 7 x64 system tells you nothing.

It was never written to support 64 bit and is no longer being developed. Last version was published in 2006-ish? I believe. Notes on the download page state:

It runs on Windows XP (32-bit) and Windows Server 2003 (32-bit)

Solution 2:

If you suspect a rootkit, don't waste time trying to find it. Wipe and reinstall the system.