I have run into this issue a few times, and decided that I needed to document this since I keep forgetting the procedure. I have had a situation where I have checked and double check my DNS modifications and no matter what I do the changes do not seem to have taken effect on some Windows clients. Well, it turns, as it usually does, that it just takes a simple command to resolve the name properly:

ipconfig /flushdns

I know this works on Windows 7, Windows 2003, and Windows 2008.

Another useful option if registerdns. If you change the IP address of a server and need it to update in your Windows DNS use:

ipconfig /registerdns

If pinging from a Windows client, you may need to flush your client DNS cache to recognize the address change.