Is it safe for me format my cloned internal boot drive?

[Wildperson]

After the latest Steam sale, I realized that I had a mere 20 GB left on my 650 GB hard drive (Drive C). So yesterday, I purchased and installed a Caviar Black 1 TB (Drive D). Given that the new hard drive is faster than my old one (7200 rpm vs. 5400 rpm), I would like to boot windows from it, and play Steam games off of it. After installing it, I formatted and created one partition on it that took up the whole terabyte (or more accurately, 950 GB). I wasn't too sure how to go about booting off of it, so I tried installing windows from scratch onto the drive. This unfortunately produced a host of errors, so I formatted it once again, and downloaded Macrium Reflect, a disk cloning software that I saw as recommended online.
Annnd present day: I cloned all the contents from drive C onto drive D. In the process, Macrium Reflect created a separate partition on drive D to put the clone. After the clone completed, I expanded that partition to once again be one large partition. So now, as far as I can tell Drive D is an exact clone of C, but with an extra 300 GB on it. I'd like to use drive C for only my music, videos, and other files/documents. I've dreamed up the idea that I can just format drive C, and since drive D is a clone, there's no reason that I would be messing up my system files in any way, but I also don't consider myself a genius in these matters.

So my overall question is this: If my second hard drive is an exact clone of my first hard drive, which is what I've always booted from, am I safe to format the first hard drive?
Will there be complications? How can I set the second hard drive as a default boot drive? Or will it do it automatically?
Thanks in advance. I've never messed around with hard drives and partitions and boot drives and whatnot before yesterday, so I would /really/ appreciate some advice.

~Wildperson

EDIT: I'm not sure if it'll make a difference, but here's my system specs:
AMD Athalon X4 2.6 GHz
6 GB DDR3 RAM
WD Caviar Blue 650 GB HDD
WD Caviar Black 1 TB HDD
AMD Radeon HD 6870

Let me know if there's anything I'm missing that would help.

 

[Paperdoc]

You can do what you want. To be safe, do it in stages this way so you can verify it's all working.

1. With power disconnected from your machine, open it and disconnect the SATA data cables (the thin 7-conductor ones) from both drives. Now take the one that was on your old drive, and plug it into the new larger one. Do not connect a data cable to the old drive. Close up, turn on, and go immediately into BIOS Setup.There you should see your one new HDD and not the old one. Go to the screen where you set the Boot Priority, and make sure that this HDD is the one you are booting from. Save and Exit, and the machine should boot up normally with one large C: drive of about 930 GB total capacity.
2. Check the whole thing out for a day or two or more. Make sure you are happy that everything you need is there - in other words, the clone copy is complete and working perfectly.
3. Now shut down and disconnect. Go Inside and reconnect the old HDD to the second SATA port (the one you originally had connected to the new HDD.) By doing this, you have interchanged which drive is connected to which SATA port. Close up, power up, and again go immediately into BIOS Setup. You should see both drives detected. Go to the Boor Priority Sequence screen and make sure the new larger drive is still the boot drive, and the old smaller drive is NOT any part of the possible boot sequence. Save and Exit, and it should boot normally again. Now you will see the smaller drive as D: with all its old contents.
4. I assume at this point you do not need to preserve anything on the old drive (D: ) because it's all on the new drive anyway. So use Windows' built-in tool Disk Management to examine the drives in its lower right pane. Make SURE you are operating on the older smaller drive. First, Right-click on the Partition on that drive, and choose to Delete it. If there is more than one Partition, delete them all. Once it is all Unallocated Space, right-click again on it and choose to Create a Primary Partition, but it does NOT need to be bootable since you're only going to use it for data. You should ensure the size is the entire disk space. If the choices are showing now, also set up the Format options - use the NTFS File System and let it do the Full format, which will take MANY hours, so just find something else to do while it works. When it's all done, back out of Disk Management and reboot. Your system will have the large C: drive to boot from containing all your old stuff still, and an empty D: drive ready for data.

 

[Wildperson]

You can do what you want. To be safe, do it in stages this way so you can verify it's all working.

1. With power disconnected from your machine, open it and disconnect the SATA data cables (the thin 7-conductor ones) from both drives. Now take the one that was on your old drive, and plug it into the new larger one. Do not connect a data cable to the old drive. Close up, turn on, and go immediately into BIOS Setup.There you should see your one new HDD and not the old one. Go to the screen where you set the Boot Priority, and make sure that this HDD is the one you are booting from. Save and Exit, and the machine should boot up normally with one large C: drive of about 930 GB total capacity.
2. Check the whole thing out for a day or two or more. Make sure you are happy that everything you need is there - in other words, the clone copy is complete and working perfectly.
3. Now shut down and disconnect. Go Inside and reconnect the old HDD to the second SATA port (the one you originally had connected to the new HDD.) By doing this, you have interchanged which drive is connected to which SATA port. Close up, power up, and again go immediately into BIOS Setup. You should see both drives detected. Go to the Boor Priority Sequence screen and make sure the new larger drive is still the boot drive, and the old smaller drive is NOT any part of the possible boot sequence. Save and Exit, and it should boot normally again. Now you will see the smaller drive as D: with all its old contents.
4. I assume at this point you do not need to preserve anything on the old drive (D: ) because it's all on the new drive anyway. So use Windows' built-in tool Disk Management to examine the drives in its lower right pane. Make SURE you are operating on the older smaller drive. First, Right-click on the Partition on that drive, and choose to Delete it. If there is more than one Partition, delete them all. Once it is all Unallocated Space, right-click again on it and choose to Create a Primary Partition, but it does NOT need to be bootable since you're only going to use it for data. You should ensure the size is the entire disk space. If the choices are showing now, also set up the Format options - use the NTFS File System and let it do the Full format, which will take MANY hours, so just find something else to do while it works. When it's all done, back out of Disk Management and reboot. Your system will have the large C: drive to boot from containing all your old stuff still, and an empty D: drive ready for data.

That's completely brilliant. Thank you!

 

[Wildperson]

Best answer selected by Wildperson.