merging two partitions..don't want to goof!

Okay..kinda messed up here...when I originally installed XP Pro on my new hdd, I formatted the drive into several partitions, with XP going on one with 5 GB...and the other software going on another partition...but I soon realized that some of the files from the software was still being put on the XP partition and was quickly filling up that partition. So...I decided to just start over...re-format the hdd....and increase the XP partition to 20 GB and re-install Xp ( which required me to call MS and get a new key code). I was just gonna leave the rest of the 80 GB hdd as unallotted and partition it at a later time. BUT...for some reason...I probably missed something....I was not able to wipe the hdd completely and now ....the 'C' drive is the active drive but it only has some of the installation files on it...and 'D' drive has the actual operating system on it but it is labeled as a logical drive. Now...I'm a little confused here..if the system boots from the 'active' partition...but my 'c' drive, which is 'active', doesn't have the o/s on it....it"s my 'd' drive that has the o/s on it....then how does it boot??
Also...when I turn on the computer a screen comes up with XP Pro listed twice...it asks me which o/s that I want to use...it thinks that I have XP installed on 'C' drive.
I have Partition Magic 8....have read the manual and the user guide but I sure don't want to srew this thing up....I'm hoping that I can just merge both together and anything that is duplicated or not needed will just go away :confused: :confused:
I have a hard time getting my little brain to fully understand this partitioning stuff...primary, extended,logical,...etc...

You won't be able to merge them like you're thinking -- Windows is going to have D: embedded in a lot of places now. If you want to clean things up, you're looking at another reinstall.

To get a clean start when you're reinstalling like that, the easiest thing is to boot off the CD and delete all the partitions in Setup before creating a new one to install on.

Tuttle...thanks...as it is right now, it is not giving me any problems...just one of those annoying things. I'll probably just leave things as they are....maybe later I'll feel like messing with it.