right
one will deal with your replies in no particular order...
for sharing over a LAN each machine should be password protected and have an account on the sharing PC (server).
browsing won't work sometimes ... too complex to go into ... and even worse XP to Vista (vista to XP is far easier)
... usb drives can be odd in that they sometimes change letters when they or a system is restarted ... immediately messing up all shares.
NTFS allows share properties to be set - so is more secure than a fat32 drive (and it will try to hang on to the letter)
Vista is a little sniffy about sharing ... so you need to be set up right.
The N&SC lets you tick boxes
http://windowshelp.microsoft.com/windows/en-us /help/e20e6875-7210-47bb-bf19-5c60e6ae86151033 .mspx
http://www.home-network-help.com/simple-file-s haring.html
Sharing discs if frowned upon ... better control if you create a folder and share that (even if everything is in it) ... because windows uses the root for system files - it sees disc shares as a vulnerability.
Also you need unique computer names but the same workgroup name within your lan
It's not difficult ... but there are lots of elements that need to be in place
finally if you should map to a network drive ... to make it permanent
to map ... you should enter the path as follows
\\servername\folder (servername and folder should be replaced with real values)
and don't forget to tick the reconnect at logon box
finally the switch on sequence MUST be usb discs, pc - and not the other way round.