Snow Leopard DVD not working
I have 10.5.8 currently - Today my installation DVD for Snow Leopard (10.6.3) arrived in the post. The DVD is not working in my iMac when I put it in my disk drive. When I put it in, after about 15 seconds, the computer ejects it again.
I've tried the CD facing both ways, but there has been no different result.
I've checked that my Mac has all the other criteria needed to install Snow Leopard, and it meets all points.
Is this a hardware, software, compatibility issue?
iMac, Mac OS X (10.5.8)