>For a start: http://windows.microsoft.com/en-US/windows-vista/Enable-file-and-printer-sharing
>
>With Win7 there are some extra things to look at:
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>1. On the laptop, in Network and Sharing Center check that the wireless network is either a Home or Work network. If it's Public, access is restricted.
>
>2. It's easier to share stuff on a Win7 Home Premium computer if it's in the Public Folder, or a subfolder of that
>
>3. If you are using a non-Microsoft antivirus/security suite on the laptop, you may need to check its configuration to allow file sharing
>
>4. You may not be attempting to log on to the laptop correctly:
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>- it sounds like your main PC is on a Windows domain, and the laptop is not
>
>- as an example, let's suppose your domain is "LX", and the domain account you usually use to log on to the main PC is "MFournier". Also, that the laptop's NetBIOS name is "Laptop", and the account you usually use to log on to it is "Michel"
>
>- it sounds like you may have created an account named "MFournier" on the laptop to try to get things to work
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>- it's important to realize that all Win7 computers effectively are on a "domain". If it's not a true domain that has a Windows domain controller, then it's the name of the computer itself. The laptop's "domain" in this example is "Laptop"
>
>If you're trying to map a drive on your main PC to a share on the laptop, and you're asked for a user name and password, by default your computer will assume an LX domain account unless you explicitly specify otherwise.
>
>If you type in "Michel" as the account name, then the main PC will send "LX\Michel" to the laptop for authentication, which will fail because that account doesn't exist there. Instead, you should use "Laptop\Michel" as the account name. Or, if you've created an "MFournier" account on the laptop, you could also use "Laptop\MFournier".
>
>Because many people aren't aware of the differences between domain and local machine accounts, earlier versions of Windows would attempt a secondary logon to try to make life easier for end users:
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>- in the example above, if you tried "MFournier", then "LX\MFournier" would be passed to the laptop and would fail
>
>- then, Windows would automatically try "Laptop\MFournier", which *might* work if that account exists, and its password is the same as the one for your domain account "LX\MFournier".
>
>I don't know if, for security reasons, current versions of Windows still include this convenience feature. So, best practice is to use "MachineName\LocalAccountName" if you're trying to log on to a remote machine that's not on the domain. That should always work as long as appropriate permissions are in place.

Thank you for a very detailed message

When I tried to connect using the account I created on the laptop, I did try with the Laptop\Michel syntax as well as 192.168.111.111\Michel syntax, where the IP would represent the real IP of the laptop. It probably did not work as, as you mentioned, maybe the setup was Public. I will check that and will let you know.