Depends on the RAID controller, and if your software supports this.

In general 12 Gb should be enough if you clean it up.

I'll find the clean up FAQ from leew


I hope this helps !

Leew, one of the key experts here has some great pointers on creating space in the system drive, perhaps with it you can create enough space.
http://www.lwcomputing.com/tips/static/bootdrivesize.asp

Well, there is 1GB free on the C:\ drive, and when I try to install VMWare, I get a Windows Installer error (112) "Not enough Disk Space"......That pops up after I click on the install file before I'm even prompted to choose the installation partition!

I use a bootCD with "Acronis Disk Director Suite" with this you can shrink the 2nd (D:) partition but remember to make the free space available in front of the 2nd partition in after the 1st partition (in between them). After that you can resize the 1st partition to take up the free space so that it grows bigger.
After this is all complete you SHOULD run a CHKDSK to check filesystem.

If you do not have Acronis, or such, you can do this with a linux liveCD.
Example take a Ubuntu LiveCD and let it boot up Once inside the desktop click start and choose run command, type in: gparted

Resizing is simple with Boot-It NG.   Just download the free demo version  (http://www.terabyteunlimited.com/bootit-next-generation.htm ), which is an exceptionally good partition management tool; and use it to do the following:

(1)  Resize D: to free up some space
(2)  "Slide" D: to put the free space adjacent to C:
(3)  Resize C:

Done :-)    You can use this technique to make C: as large as you want.

Here's a bit more detail on the process:
https://www.experts-exchange.com/questions/21929035/Bootit-NG-and-Partition-resize.html

Note in particular the pictorial example of what you need to do here:
https://www.experts-exchange.com/questions/21929035/Bootit-NG-and-Partition-resize.html#17169507

... note that you do not need to install Boot-It => just create a bootable CD;  then boot with it; select CANCEL at the first prompt; then OK;  then go to Partition Work & do the resize/slide/resize operations outlined above.   The resize operations will be very quick;  the "slide" will take a good while (it's got to move all the data on D:).

DO have Paragon Partition Manager, but can't quite seem to figure this one out.....

Do you have personal or server version?
If you have server version, after you watch this demo, you will definitely know how to resize your partition. All you have to do is boot the Advance recovery CD and follow the steps:
http://www.paragon-software.com/export/sites/paragonsoftware.com/images/screenshots/en/pm-server/2_redistribute_free_space.swf

K

Hi tenover,
run Partition Manager and in its main interface right click on D: and choose Move\Resize.
Then in opened window catch the left border of volume with mouse left click and drag it to the right. Free 5GB space as you need and apply changes. When D: drive is not locked by running applications the operation should complete in Windows. In Partition Manager 9.0 you can see the files locking partition and close them manually.
Ok, free space is taken and located between C: and D:
Now right click on C: and choose same Move\Resize option. Then catch the right border of partition and drag it to the right so your free space block would be allocated to C: volume. Apply changes and in few moments operation will complete.
Its done. I have done this operation many times so if you have questions feel welcome to ask.