Help- Cleanup HD partitions after W7 install

I have Win7-64bit installed on my C: primary partition and several of the principal apps which I use already installed and working as well. :)The C: drive currently has three partitions:
-The first (365G NTFS) healthy primary one has the OS, data files, and everything else.
-The second (100G ???) healthy primary partition has no assigned drive letter. This
was origially space reserved for installing XP-Pro (just in case...)
-The third (17MB ???) Unallocated (not sure how it got left over.)

This is running nicely and backed up to external IOMEGA HD with Win7 Backup,and
Restore disk created.
I also have the full Win7 Home Premium 3-install disk which I plan to use for two other PC's in-house.

Without reinstalling any SW (if possible) I'm considering installing a new (160G ?) HD, set it up as the primary boot/OS drive and move Win7 onto it. Then change existing drive to D:.
Also then keep installed apps either on "new" C: drive with the OS (would bigger one be good idea?) or on renamed D:, and data files, pics, etc on separate drive - either with apps or third drive (NOT the IOMEGA, which is for backups)
What is the best way to proceed? Does having the OS, apps and data files on separate drives give a performance advantage? (Seems like def easier to image for B/U)
I"ll try to post a pic of my current Disk Management window if I can figure out how...

Sounds like a job for the "clone" function in Acronis. You can download a 30 day trial version and try it.

The alternative is to make images of existing partitions and then restore them to the new HD. Cloning simply "transfers" your existing C partition to the new HD without an intervening image.

It's good practice generally to keep your OS and apps on one partition and data on another, but plenty of people put everything on C. Some would separate the OS from apps, but that's of minimal if any benefit.

If I were going to use cloning, I might consider first shrinking the existing C to a size smaller than the new HD. If you have a 360 gig partition and try to clone it to a 160 gig new drive, I don't know that it would be allowed.

I'd generally advise you not to buy a new drive and then use it ONLY for the OS. If you need a new drive, get a good fast one and put your OS and all apps on it at a minimum. That would typically require only 40 to 80 gigs.