Mercurial-1.9 (32-bit exe) / Mercurial-1.9 (64-bit exe), does not need admin rights to install (InnoSetup based).
http://mercurial.selenic.com/release/windows/Mercurial-1.9.exe
Like TortoiseSVN, we recommend to turn off the indexing service on the working copies and repositories, and exclude them from virus scans. The following installers can be used from Windows XP on: