Be careful on spanning drives, as first, they must be dynamic, and second (and more important) a loss of a piece of a spanned drive destroys the data on the entire spanned area. In other words, a spanned drive, while it gives you a bigger drive space, also has a higher disaster cost! Note also, that you cannot extend a system volume (C: in this case) or a boot volume (also C: in this case), so spaning the drive is not an option for your problem (C: is out of space).
Microsoft does not allow you to play games with the system and boot partitions, although some third part applications will actually do it successfully. While you can install the OS in a volume created on a raid array, I do not believe (Not totally positive on this) you are even allowed to install the OS onto a spanned volume, it has to be on a volume on a single (virtual in the RAID ARRAY case) drive. Win 2000 looks at a RAID ARRAY (hardware version) as a single drive, which is also why you can mirror two RAID 5 drive configurations, regardless of how many drive physically constitute the arrays.
What it all boils down to is that good planning must go into the original setup of the system. Everything you are trying to do here is just stop gap, it does not fix the real problem (that the system was not designed correctly), especially since it is also an Exchange server. Your disaster is just waiting to happen.
By the way, many applications that do not show up in the add/remove applications actually have an uninstall program installed in the directory where they were originally installed (look under the start programs, and see if the applicaion lists an uninstall there).
In addition, just because programs show up under the program files directory, it does not mean they are actually installed (Front Page is one of these), it is just a place holder, especially for Microsoft programs. Check to see if there are content files actually installed on the drive.
I highly agree with all the comments with re-doing your system. I would NEVER build a DC + Exchange on a system that was not a RAID 5 (or at very least a MIRROR SETUP) for both the OS and the EXCHANGE portions. These are two very critical systems, and need the best redundancy available. Also, as I stated before, DO NOT PUT the EXCHANGE database on the same partition/volume/drive space as the OS, and do not use the Exchange computer for other functions like DNS, DHCP, etc., as you will suffer a performance hit.
While Exchange 2000 wants to be on a DC with the AD, I would not want this to be the only DC in the system either, if at all possible. (Note, with the cost of simple systems today, building a simple second DC, single processor, no raid, etc., is dirt cheap when compared to the cost of the disaster when the company stops functioning because the only DC is down and no one can work. Use a desktop if all it is doing is providing the survival capability, (total cost maybe $2000?).
Remember, COST CUTTING AND POOR PLANNING = MASSIVE PROBLEMS AND MASSSIVE COSTS LATER! (Pay me now, or pay me later!)
HTH
David