Windows 7: Sharing Problems

I am at my wits end on this. I have several computers that I would like to be able to network. All 3 of them are connected to my router and all 3 can access the internet. But if I want to transfer files from one computer to another, I can see the other computers on the networking page, but if I try to access them I get asked for a username and password. WHAT USERNAME?? WHAT PASSWORD??
I never set up any passwords. Anything I put in there gets turned down. I can pull up a password on one machine, but if I type it in on the other machine, it still won't let me in. And I still don't know what username to put. I tried the computer name and the login name, for which I have no password set and I'm still locked out. Do I have to transfer files with my thumb drive even though I should be linked?? BTW, when I was running XP on all 3 machines, they networked just fine.

TC

Are you using homegroup or workgroup?

OK, I had similar problems, and managed to not have to resort to sneaker net. This is do-able, and with the help of the folks here, fairly trivial.

Now, are the computers all running WIndows 7? Are they part of a Homegroup?

We're going to need some more info on your lash-up, but believe me, it can be done.

2 of them are running Win 7 build 7600 and the last one is running
Vista Ultimate. And I put them all on Homegroup. I can still boot back to XP on 2 of them, but it's a pain. Is there not a simple way to get this to work???

try this:

goto network and sharing center

choose homegroup and sharing options

changed advanced sharing settings...

turn off password protected sharing