When you visit a website, Windows 2000/XP/2003/Vista tries to speed things up by placing the DNS information about that site, into a DNS cache on your PC.
You see the DNS Windows 2000/XP/2003/Vista cache stores BOTH negative and positive entries. The positive entries are those that the DNS lookup was successful and you could connect to the website.
Negative entries are those where the DNS lookup failed and you could not connect to the website.
A problem can arise here because if the DNS cache hold a negative entry and the website you want to view is now OK to view, Windows XP will still give you a DNS error!
First of all you need to flush the local DNS cache with the following command in a command prompt
c:> ipconfig /flushdns
Block Negative Entries
If you want to block cache Negative Entries in Windows XP you need to add a new DWORD to the following Registry key
Note :- Before doing any changes to the registry please take a backup of your registry
This will now ensure NO negative entries are stored in your windows xp machine.Hope fully it will work for windows 2000/2003/Vista