I found a strange thing here. From xp, I always user username "administrator" with no password and that showed me the message when I tried to access share folder on win 7 " \\xx-pc is not accessible. You might not have permission to use this network resource. Contact your administrator of this server to find out if you have access permission." Then I created another admin account name "test" on xp, and this time, I got the prompt to enter username and password. I entered the account/password on win7, I was able to access my share folder!!!! WHY?? This will never happen if I access another xp machine!! only happen when I access win7

Hi, you must allow user Administrator. This user is disabled by default. Start - Run - compmgmt.msc

I already enabled the default administrator account, but it didn't make any difference