How are you setting up your 'virtual hosts' ? If you want to set up a domain-like host to point to the localhost, edit your hosts file. Default location for this file is:
Most unix os's:
/etc/hosts
Windows 9x:
c:\windows\hosts
Windows 2000 (XP?)
c:\winnt\system32\drivers\etc\hosts
All that needs to be in this file is:
127.0.0.1 my.domain.com
(seperated by tabs) and your os should resolve it to local. I don't have a dial-up connection here to YYMV.
Hope that helps!
-Chris