not sure how sharing works in windows 7 but in winxp make sure you don't have an administrative share (with a dollar sign $ in front of share name);
tried disabaling share then renabling share and give it a label?
If it's a non-secured share have you just tried:
username: guest
password:
sudo curlftpfs -o allow_other ftp://user:pass@your_home_PC_IP [mountpoint]
[fullscreen] mplayerx /path/to/file
or
[window mode] mplayerxw /path/to/file