Administrator log in

I have two computers, both have Win XP Home, NIS 2007 and IE7. One computer
is wireless, one hardwired and both running through a Linksys Router. I can
see both computers on the network from either computer. I can access the
computer 2 from computer 1. However, I can not access computer 1 from
computer 2 (Do not have permission to access). Computer 1 has 2 users and
computer 2 has 1 user. I have read all the things I can find about file
share. First off, on neither computer can I find "Simply File Share". Second,
when I log in as administrator in safe mode on the computer 1, I can't access
the network to add computer 2 into the permissions. Now is there a way to get
administrator to come up on the Welcome screen in normal boot? Is there a way
to allow computer 2 to access computer 1? I'd appreciate any help. Thanks.