1. If you bought the CD, the key should have come supplied. With OEM disks, you are provided with a key that looks like this:
I have never bought an off-the-shelf version but I imagine it shouldn't be hard to find in the package contents. If you honestly don't have a key that's 25 alphanumeric digits in groups of five, then your only option is to call Microsoft and buy a new one. The key is more important than the disk; the disks are all identical.
2. As I hinted to, partitioning can be done in Windows setup.
This website's quite a good guide. The important points to remember is to delete the existing partition, create two partitions to fill up the disk (see
here), then select one to install Windows onto.
3. Most drivers install like programs, but it's best to check the device manager after you've installed everything to see if anything's got a yellow question mark by it, meaning its driver's not installed.