okay, thank you, but where exactly can I find the .bat file. I looked but I don't think I have seen anything with a .bat extension.
Now, that question will only apply if this one is a no.
Is this what the interpreter should look like.
If you've downloaded the '.zip' version of build 820, unpack it to any location. If you unpack it to (for example) C:\somewhere, then you'll find the installer.bat in the C:\somewhwere\ActivePerl-126.96.36.1990-MSWin32-x86-274739 folder. Then it's just a matter of doing a 'cd' to C:\somewhere\ActivePerl-188.8.131.520-MSWin32-x86-274739 and entering installer.bat. If it prompts you to install perl to a location that contains a space (eg C:\Program Files) don't let it do that. Instead opt for a location that doesn't have any spaces - eg C:\Perl. Otherwise, accept the defaults.
Then run perl -v to check that all is well. All being well, you can then remove the C:\somewhere\ActivePerl-184.108.40.2060-MSWin32-x86-274739 folder as it's no longer needed.
If you have downloaded the '.msi' version, then it's just a matter of double clicking on it to proceed with the installation. (Again it's best not to accept any default that wants to install perl to a location that contains spaces.)