I'm sharing a pc with my friend and we need to set up two admin accounts to use properly the pc. We have Win 7. The problem right now is that the first admin can view the folders content of the second admin and viceversa. I know that we can simply create two user and set up folder permission but we need admin accounts to manage the pc properly. Any solution?
An administrator on Windows can always access any files regardless how you set permissions for them. The only way to protect the content from an administrator is to encrypt it.
You could use a third-party tool like TrueCrypt to create a volume for all your 'secret files'.
If you want to use Windows tools only. You can encrypt file by file using 'Encrypted File System (EFS)' which is built into Windows. The first time you are using it, a digital certificate is created which you should backup into a secure offline location. If you forget your windows password or loose the certificate backup (or its password) you wont be able to access your files yourself any more.
This has the advantage over TrueCrypt that you don't need to enter a password to use your files because your Windows account holds your certificate. However even though other administrators can not see the content of your files, they can see the file names and can delete the files.
When using TrueCrypt other admins can't see the file names but they can still delete the whole true crypt volume with all your data. A TrueCrypt container is also easier to copy to other computers because you don't have to copy the certificate and you can store it on a FAT formatted thumb drive. EFS files only work on NTFS.
Before making a decision you should learn more about these options and test them out.