To fully optimize a Hard Drive, any hard drive, the program doing the optimizing has to have exclusive access to the files. If the HD you are trying to optimize is the one from which the machine is booted, then the OS is busy doing its thing so the drive cannot be optimized. (You cannot move system folders while they are in use)
OR
If the drive you are trying to optimize is the one on which TTPro is launched from, you cannot optimize because TTPro is using the HD.
The Warning message you got said that you could not optimize because this was the Startup disk and that TTP was launched from it. (that's three strikes and out) What was the third strike? You didn't read the instructions that came with TTP that said you had to boot from the CD if you only had one drive OR you had to create an E Partition to boot from.

Try booting from the CD and you will find that it will now work as advertised.

P