Actually there is 2 connected problems:
1. I have several computers with XP Pro (patched up to date) and hp Install Network Printer Wizard 6.0, connected to hp LaserJet 1320n and DesignJet 800 printers.Everything seems to work, but with one quirk - after 1-2 hours after powering on, computers disappear from "My Network Places". They can be pinged, their network shares can be accessed directly, they can use network - but they are invisible. Restarting computer helps, restarting Computer Browser service helps, even restarting AD controller helps. BTW, does not matter if Computer Browser service is running or stopped - after some time computers become invisible.
"Uninstalling" INPW, deleting TCP/IP port and printer drivers helps permanently.
2. Tried to uninstall INPW 6.0 and install 5.0 version. Uninstall seemed to work, at least it was removed from Add/Remove programs. BUT at print server properties 'Ports' page there was still line "hp standard TCP/IP port". Nevertheless, I installed 5.0 version and got the same problems. Tried to uninstall 5.0 version and there the fun begin: "This version of the HP Install Network Printer Wizard is older than the one currently installed on your system. Are you sure you want to replace the existing (newer) version with this older version?". Huh?! I uninstalled 6.0 version before. And no, i can not uninstall 5.0 version.
So the question is: how to solve problem with invisible computers and how to completely uninstall INPW, so i can try another version?