HI.....
Is the system that is unable to get access to system, asks for user name password to accesss your machine....................' then '
make a new connection on the system you havent made one on...if that doesnt work then make a new connection on the other one...
make new conn >setup a small home or office n/w >
when it asks for a method of connection... select "other" option the proceed , then "this computer belongs to a n/w that does not ahve an internet connection "
then fill up ur computer description ...now comes the most important part....
"turn on file and printer sharing" >> just finish the wizard
and restart your PC....
u might argue u have already done that...try doing this again....

it works
hope it does..that is how i make it work...
PS: try doing this on both th systems