Password ageing in Windows 2008 Server Standard edition (the one I generally use) is set to automatically requre passwords to be changed after 42 days…obviously a Douglas Adams fan responsible for that bit of the codebase!
NOTE – I don’t have access to other version of Windows Server (2003 or 2008) so I can’t speak for them, but I imagine it’s the same on them too.
That’s annoying for home use, where I have tons of VMs for research that I use periodically, so I asked my brother Steve how to stop this happening and he gave me some simple instructions…
First start the Local Security Policy editor by typing secpol.msc in the start/run box..

and then select Account Policies / Password Policy on the nagivation tree on the left. On the right hand side select Maximum Password Age and set this from the default of “42″ to “0″. You’ll notice it now says “Password will not expire” above the value “0″.

Seems to have done the trick.
Kinda handy having a brother who’s an MCSE and a VCP too. Useful when I get stuck with OS or VM stuff for my Oracle research!
By the way, if anyone happens to be looking for some skilled contract resource in the Virtualisation field (VMWare, ESX Server etc…) then Steve has just become available…please feel free to contact me, or Steve, via his website