Today, i downloaded and tried to install Visual Studio Service Pack 1 (SP1) RTM but it refused to work properly on my PC.
I was always getting an error that the file is not matching the version i have etc, so i tried to figure out what is wrong with my Visual Studio installation.
Although the Visual Studio team says that we have to uninstall Service Pack 1 (SP1) beta prior to SP1 RTM installation (i found it after searching the team's blog),
they don't say how and there is not even an option on Add/Remove Programs to remove it.
You have to uninstall it manually,at least this is what i did,by executing msiexec /uninstall {2F899F40-A951-453D-ACAB-F7314D4DCB2C} or msiexec /i {2F899F40-A951-453D-ACAB-F7314D4DCB2C} on the command prompt.
If it doesn't work, try extracting the VS80sp1-KB918525-X86-Beta-ENU.exe from the Self-Extracting file you downloaded and run it passing the /uninstall parameter, like this "VS80sp1-KB918525-X86-Beta-ENU.exe /uninstall", on the command prompt.
During the uninstallation (it takes a while) you will need Visual Studio DVD (or CDs) to complete it successfully.
You can now install the Visual Studio SP1 RTM edition.

* The above post describes what i did on my PC to install SP1 RTM, i'm not sure if it applies to all SP1 Beta installations out there or if it was just my bad luck.
Whatever the situation is , i'm sharing this in case someone else has the same problem like i did.