I share a printer under vista and want to use it as network printer under win 2000 .But 2000 can not detect printer. (I also disable windows firewall and antivirus firewall on vista).Can anybody help me?

You can see from vista PC , the other PC and reciprocal? The network works, you checked "turn on network printer"? Maybe you have a smart antivirus , turn it off !

For Windows 2000 and Microsoft Windows NT, you can use the following command:

net use lpt3 \\servername\printer /persistent:yes

This command maps the network printer to the local port LPT3. The user can then install the correct drivers for that printer as though the printer was installed on LPT3. If this is done, the printer on LPT3 is redirected when the user connects to the Terminal Services session. This also works with PT1 and LPT2, as long as there is not a local device on either of these ports.

For Microsoft Windows 95, Microsoft Windows 98, and Microsoft Windows Millennium Edition (Me):

Right-click on the network printer in the printers folder and click Properties. From the Details tab in the Printer Properties box, click Capture Printer Port. This action can enable you to select the LPT port that you want to map to this network path.

The preceding workaround is useful in environments when a user opens a session to a Terminal Services computer on a remote network (for example, across the Internet) and wants to print back to a printer shared on the local area network (LAN).

Microsoft Windows Help And Support

Open the properties for the printer, select security and add all the users, giving them rights to manage the documents/printer. The next time they connect, they will already be authenticated and be able to use the printer.

Thanks to Francisabey.