I have a computer with XP Home that I share some files on my network.
I have used a laptop with xp home with my logon and been able to access the files on my network.  I got a new laptop with windows 7 home premium and I can see the files on my network, but when I try to map the drive I get a message that says network error: you do not have permission to access. I have check all of my sharing and I have network discovery on, file and printer sharing on, sharing in the public folders sharing section on, and password protected sharing on.  I TRIED the password protected sharing off and that didn't change anything. I have turned off my firewall, I still cannot map it. The laptop that has xp will connect with the same log on that I have on the windows 7 laptop. Any help please!
Are you having issues connecting from Win7 to XP or vice versa?

Which ever machine you are connecting FROM that gets the error message, means the security issue is on the OTHER machine.
So connecting from Win7 to XP and you get the error, then you need to check the file/folder sharing permissions on the XP machine.

Also check that all your computers are on the same network, if memory serves XP defaults to HOME and Win7 defaults to WORKGROUP.It is Windows 7 connecting to XP. I checked the XP machine and made sure the LOGIN had full control of the file I am trying to map.
I also checked to make sure they were on the same network. I have a laptop with XP on it and the same logon and it will connect and open the files, but the Windows 7 with the same logon gets the message that You Do Not Have Permission to Access.just checking but did you check the share permissions? There is a difference between share permissions and file and folder permissions.  I check both and they are set. I have a laptop with XP and it has the same logon and it connect fine.
Check your NTLM version settings on the Windows 7 machine.

To change the NTLM version in windows 7 follow this:
1. CLICK start
2. type gpedit.msc (if USING classic start menu click run then type gpedit.msc)
3. navigate to Computer Configuration -> Windows Settings -> Security Settings -> Local Policies -> Security Options
4. Scroll down the list until you see 'Network security: LAN Manager authentication level'
5. Double click and change the level to 'Send LM & NTLM - use NTLMv2 SESSION security if negotiated'