Asus Laptop Partitions

So I just got a ASUS laptop for college next year and I am extremely satisfied with it, exceeded all my expectations and changed all negative notions I had regarding laptops but there is one flaw ive encountered. My HDD is partitioned into C: and D: drives with the operating system being on C and Data being allocated to D. Im not unfamilair with this practice but what is odd to me is that all of the user and program files are located on the C: drive so all my installed programs and downloads are automatically placed under the C: drive which is only 75 gigs with much less available due to the operating system and system files. I am now left with 7 gigs on it and I was wondering if anyone knows how to change the directories of my computer so that downloads and program installations are automatically routed through the D: drive so my C: drive has more breathing room since it holds the OS.

Any help on this would be greatly appreciated because it would be a terrible hassle to un and reinstall all the programs I have already installed that came with the computer onto the other drive

my specs are:
windows 7 64 bit
intel duo p8700 at 2.5 ghz
4 gigs ram
if any additional specs are needed just ask though i dont feel they will be

 

If you have yet to install anything on the D drive you can combine the two of them. The steps to take:

click on the windows circle at the bottom left of your computer. Right click on computer and choose manage. Left click on disk management. Right click on the D partition Delete the D partition(only if you have nothing else on the drive.) It will turn green, then delete it again. now it will turn black. next right click on the C drive and click expand. click next, next, next and now you have combined the two partitions and have a large C drive. Hope that helps.

 

thanks that does help alot, is there a way to modify the size of my existing D drive like cut it in half or something along those lines because its a hassle movie all my music off and on my computer and there isnt enough room on the C to temporarily move it there. What im basically saying is could I essentially trim the D drive down like 100 gigs so that its automatically applied to the C drive and I can leave my existing data on the leftover space on the D drive?