Reinstall Mail

I have a MacBook running OSX 5.8. I deleted the Mail application, because idiot.
I want to reinstall it BUT the Install disk has OSX Version 5.5, so when I try and install from here it won't as there is a more recent version of OSX on teh computer. I don't want to go backwards to 10.5, I want to keep 10.5.8 and just add Mail.

How do I do that then?

You should be making backups. Time Machine is included with your copy of Leopard and will make a full backup of all your data. There are several ways to get back your Mail application but the easiest may be to extract it from Disk 2 of your Leopard disk set. You will need special software to do that though. Download "Pacifist" from here.

You might be better off upgrading Leopard to Snow Leopard but since you didn't tell us which Mac you have, we have no way of knowing if your Mac can be upgraded. You can buy Snow Leopard direct from Apple for $19.99.