Map Network Drive

Hello.
This isn't critical but I'm very curious.
I've mapped some drives and folders on my laptop (Wireless Network
connection) and there's something weird happening. XP sp2.
2 PCs Both have an additional drive each.
Everything that's shared can be accessed with no problem.
I've mapped both additional drives on the laptop and it accepts them.
but one of them when I click the mapped drive, a window opens saying
'OPEN WITH' and then lists all the programs/software, like Word, Internet
Explorer etc.
And yet I've mapped a couple of Folders that are on that drive and the
window opens as it should.
The other Pc's second drive opens as it should. That second PC has the firs
PC's second drive mapped and it opens as it should there.
Any ideas?
J