Help! on Dual-Boot and Making another Drive

[TheGW]

First, I need help on Dual-Booting.
How do I do that? Some guides on Google.com are so misleading and not Newbie Friendly.
I'm having also a hard time on understanding about Dual-Booting.
What are the risks? What will happen to my other OS?.
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Second, As I noticed, my PC has one Hard Disk inside my CPU Case, but in "My Computer" I can see two (2) Local Disks. C (18.7 Space Total - 9.04 Left) and D (18.5 Space Total - 9.93 Left), I'm wondering how do I make another one? Can I still make another even if it's already more than half full?.

Thanks in advance.

[endrien]

First, I need help on Dual-Booting.
How do I do that? Some guides on Google.com are so misleading and not Newbie Friendly.
I'm having also a hard time on understanding about Dual-Booting.
What are the risks? What will happen to my other OS?.
-----
Second, As I noticed, my PC has one Hard Disk inside my CPU Case, but in "My Computer" I can see two (2) Local Disks. C (18.7 Space Total - 9.04 Left) and D (18.5 Space Total - 9.93 Left), I'm wondering how do I make another one? Can I still make another even if it's already more than half full?.

Thanks in advance.

What OS are you trying to install? Don't do anything to your D drive as it is what your computer manufacturer has used as a system backup because they don't want to give you Windows Disks. It depends on what Os your going to install, once you tell me that I can help you.

[TheGW]

What OS are you trying to install? Don't do anything to your D drive as it is what your computer manufacturer has used as a system backup because they don't want to give you Windows Disks. It depends on what Os your going to install, once you tell me that I can help you.

Well, the story of my D Drive.
When I bought my PC, it contains these set of installer in a hidden folder:

1. Microsoft Encarta 2006 Premium
2. Microsoft Encarta Kids 2006
3. Microsoft Office Professional 2003
4. Internet Explorer 5
5. Windows Media Player 10
6. And some Games (SC and SC: Brood War, WC3: RoC and WC3: TFT, Battle Realms, D2 and D2: LoD, and some other stuffs.)

I actually managed to install Office Pro, IE5, and WMP10, I didn't thought Encarta would even require the other files to run. (So I backed up the Games only) and Reformat the Drive.
Now my Encarta won't work at all, Only the Dictionary Tool. (I'm planning to uninstall it though later on if my C gets too low around 5.0 G

The OS that I'll be installing is Microsoft Windows 7, I got the DVD from the Professional Developers Conference 2008 that our Professor attended to last last month.

I'm trying to use it for purposes like:
1. How good does it work on lower systems.
2. Programming support for us students.
3. And Game compatibilities.
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BTW, currently installed in my D Drive are FlyFF, BitTorrent, AuditionSEA, and PeaZip. All in all they consume more than half of the Drive as I stated before.
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Edit:
I also don't have my License for XP.
(Can't afford LOL!) But I got Windows Vista Home Basic 32 Bit Edition + License, but it's only for my Laptop.

[vimick]

Second, As I noticed, my PC has one Hard Disk inside my CPU Case, but in "My Computer" I can see two (2) Local Disks. C (18.7 Space Total - 9.04 Left) and D (18.5 Space Total - 9.93 Left), I'm wondering how do I make another one? Can I still make another even if it's already more than half full?.

Thanks in advance.

for this look up "partitioning your harddrive" in google. this will give you virtual drives like you have for your D drive. i'd explain it better but im in class