Dual boot back to single

I have a system with one disk with one primary partition, C:, and an extended partition that conatins D:. It's set to dual boot. C: is XP64, and D: is XP32. I want to go to single boot with XP64 on its existing C:, after which I will resize C: to consume the entire drive.. The startup files, e.g., boot.ini, ntldr, etc., reside on C:\. What is the best way to proceed? Can I just delete D: and enlarge C: to consume the free space where D: existed? I imagine that I may have to edit the boot.ini, but what about other files? I run Partition Manager, so I have the means to create/remove/resize partitions.

Scenario 2: I have another system with one disk with one primary partition, C: and an extended partition that conatins D: It's set to dual boot. D: is XP64, and C: is XP32. I want to go to single boot with XP64 on its existing D: In this case, the startup files, e.g., boot.ini, ntldr, etc., also reside on C:\, but I want to remove that partition and leave existing XP64, D:, as the boot partition. How should I proceed here? Thanks!