Question : Hard Drive Space from G: drive to D: drive?

On our server we have four partitioned drives.  Right now our D: drive is running pretty close to full, but that is the drive we use as our "Storage" drive.  Our G drive has hardly been touched, and still has 193 gigs free.  What I would like to do, (If Possible) is move 100 gigs over to my D drive without formatting anything.  I think I read this was possible, just a little difficult.  Is that true?  If so, does someone have a good solution?  I have never moved space before so I guess this would make me a beginner on the subject?

If it makes a difference we have 6 146 SAS hard drives in our server, and obviously they are in some sort of array.

Answer : Hard Drive Space from G: drive to D: drive?

i suggest using Bootit-ng  : www.terabyteunlimited.com/       
for what you want to do, it is free; download it, and boot from floppy or CD -do NOT install it on the disk, hit cancel and select partition work
Now you must look at your setup; imagine it is like :
|--D--|--E--|-----F-----| End of disk space
if you want to increase the D or E size, you must free space next to it, so, to resize D: do as follows :
select F partition, and resize it (lets say it is 150 Gb, and D: = 20 GB) to 100 GB (freing up 50 GB)
then slide it, to wards the end of disk, so you have now :
|--D--|--E--|--free---|---F---| End of disk space
now do the same for E: to get  :
|--D--|--free--|--E--|---F---| End of disk space
now resize D

***bootit-ng works on all OS'es, never has let me down !