When you are logged into each OS does each OS see itself as C: ?
Or is 7 C: & 10 E: (or something other then C: )?

If 10 is E: (or something other then C: ), I'm pretty sure that some C: must exist, need not be big, necessarily, but must be there.

Depending on disk layout, as in if the partitions are C: D: E: (in that order), you may need a 3rd. party utility to rearrange things. As in you won't be able to directly have E: acquire C:'s space.

(I'm not sure offhand how flexible 10's partition handling is in that respect, but pretty sure you'd need 3rd. party.)

You would want to make sure you've got backups prior to doing any repartitioning no matter how "simple" it might be.

Was this 10 a "upgrade" (cough) from 7?

You may want to start over.
Have everything backed up (more then once is even better).
Blow away all partitions.
Install 10. (Cough. You really want to do that ;-) ?)
Split 10 (which Windows should be able to do) into 2 partitions, the second being your 60 GB partition.
Install your programs.
Copy your data back in. ...

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If, C: D; E:, & aside from the fact that I believe you'll need a C:, you may be able to delete partition D:, have C: acquire it, then resize C:, to 60 GB, then expand E:, having it acquire that freed up space.

Then you'd have a C: 60: GB & a E: 240 GB.

That might work, with Windows utilities, alone.

You'd have to back up (still), either copying D: to C: first, or restoring a backed up D: to C: after the fact.