Recovery Drive, can I trim it down?

I’m running Windows Vista Home Premium 32-bit, and besides the hidden drives I can’t access normally, I have my C: drive and my D: drive

my D: drive [name is designated as RECOVERY (D:)] is apparently used for computer backups, but I see its almost full; is there a safe way to clear that drive out so I can free it up for some fresh backups, also, since I already know how to use the Drive Manager to trim some free space off of my C: drive and turn it into a digital Hard Drive on my computer, can I use the method of trimming some free space off of my C: drive and giving said free space to my Recovery D: drive?

also, its been a LONG time since I’ve been on here, and I’m glad to be back……….or something