HELP! More Tiger to Snow Leopard

Question

I still run Tiger on my MacBook Pro, so I purchased the Snow Leopard Boxed Set, just like Apple wants us to. Studied up to know what to expect, cleaned up my computer, popped in install disc, and immediately something's wrong: When I click on the Install Mac OS X button, instead of the set up installation menu, I get one that says I need to restart my computer to begin the install process.
Not what anything I've read says is supposed to happen, but I go ahead and restart. So ... I continue following instructions until I get to the Choose the Install disk part: I get an icon with my hard drive and an exclamation point, and a note that says I need to use Disk Utility and repartition my disk using "GUID Partition Table", and that I will lose all my data by repartitioning my disk!
I really, really, really want to avoid a clean install. I just don't have the time for it. Even so, I opened up Disk Utility and can find no mention or explanation of "GUID Partition Table."
Can someone please enlighten me. PLEASE!
(After further reading - Apple needed to be more clear about this - I realize my old Core Duo process will limit the ability to take advantage of 64-bit processing and Open GL. But what does that have to do with installation?)

Answer 1

Adding a bit of background info to baltwo's replies, all Intel Macs come from Apple with their drives formatted with the *GUID Partition Table* (GPT) partition scheme. Moreover, if you repartition the internal drive of an Intel Mac with Disk Utility, it defaults to this scheme. Thus, the only way it could be changed to Apple Partition Map (APM) is if you (or someone else besides Apple) repartitioned it & purposefully selected that scheme with the "Options…" button, or repartitioned it while it was connected to some other Mac as an external drive (including with Target Disk Mode).
This may help explain why Apple doesn't mention this in the instructions that come with Snow Leopard. It is an unusual situation & should apply mostly to those with the necessary equipment to backup & reformat the internal drive again.
A bit more info: Intel Macs will startup from disks using the Apple Partition Map scheme -- in fact, the Snow Leopard DVD itself & essentially all other Apple-supplied bootable DVD's use that scheme. In that sense, it is a more universal one because PPC Macs can only boot from APM. However, GPT is more modern & flexible & a much better match to the capabilities of Intel Macs. For instance, the drive must use GPT if it is to support Boot Camp dual booting into either Mac OS X or Windows, or support most non-Apple file systems like Microsoft's NTFS & many others.
Thus, the only compelling reason to format a drive with APM is if it must be used with both PPC & Intel Macs. This obviously does not normally apply to the internal drives of Intel Macs. Sooner or later, you will probably need to return the MBP's drive to the GPT scheme, so it is a good idea to make time to do so as soon as it is convenient.