'I am trying to access a network setup by my friend with windows' - there are numerous version of 'Windows'. Are we to assume the version of your friends' PC is 'XP'? Assuming such ...
Did you, or your friend, ? ...
01. Double click on the ('Windoze') 'Desktop' based 'My Computer' icon.
02. Do a contextual click (right button, for right handed users) on the 'C', or whatever other, hard disk drive's icon - to be accessed.
03. Select the 'Sharing and Security...' menu item.
04. Click on the 'Sharing' tab.
05. Click on the 'If you understand the risk but still want to share the root of the drive, click here' hypertext link.
06. Locate the 'Network sharing and security' section, and click on the 'Share this folder on the network' and 'Allow network users to change my files' check box'es - to add a check mark to each.
07. Click the 'Apply' button.
08. Click the 'OK' button.
09. Close the 'My Computer' window.