Have OS 10.5.8. New external HD require 10.6. Can I use this? Also, can a new HD be initially used on Windows7 to store movies and then used on the Mac without confusing the HD?

Question

I have a Macbook Pro with OS 10.5.8.  I wish to get a new external HD.  The HD packaging seems to indicate that an OS of 10.6 is required.
Questions:
1:  Can I reliably use a new external HD requiring 10.6 on my 10.5.8?
2.  Does anything have to been changed/altered on either the HD or the laptop to make such a HD work?
3.  The HD would initially be used to transfer movies from another external HD, via a PC with WIndows 7, onto the new HD.   This would be a one-time event simply to get movies from a friend's HD.  Will the new HD be affected in anyway with having its first contact with a PC rather than my Mac which it ultimately will be used with?
I am not a wizard with technology. 
Please advise.
Thank you.

Answer 1

You need to upgrade OS X on your computer. The drive will have to properly formatted for a PC but be usable on a Mac. So the drive must be prepared as follows:
Drive Partition and Format
1. Open Disk Utility in your Utilities folder.
2. After DU loads select your external hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.
3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to MBR then click on the OK button. Set the format type to MSDOS. Click on the Partition button and wait until the process has completed.
Upgrade Paths to Snow Leopard, Lion, and/or Mountain Lion
You can upgrade to Mountain Lion from Lion or directly from Snow Leopard. Mountain Lion can be downloaded from the Mac App Store for $19.99. To access the App Store you must have Snow Leopard 10.6.6 or later installed.
Upgrading to Snow Leopard
You can purchase Snow Leopard through the Apple Store: Mac OS X 10.6 Snow Leopard — Apple Store (U.S.). The price is $19.99 plus tax. You will be sent physical media by mail after placing your order.
After you install Snow Leopard you will have to download and install the Mac OS X 10.6.8 Update Combo v1.1 to update Snow Leopard to 10.6.8 and give you access to the App Store. Access to the App Store enables you to download Mountain Lion if your computer meets the requirements.
     Snow Leopard General Requirements
       1. Mac computer with an Intel processor
       2. 1GB of memory
       3. 5GB of available disk space
       4. DVD drive for installation
       5. Some features require a compatible Internet service provider;
           fees may apply.
       6. Some features require Apple’s iCloud services; fees and
           terms apply.
Upgrading to Lion
If your computer does not meet the requirements to install Mountain Lion, it may still meet the requirements to install Lion.
You can purchase Lion by contacting Customer Service: Contacting Apple for support and service — this includes international calling numbers. The cost is $19.99 (as it was before) plus tax.  It's a download. You will get an email containing a redemption code that you then use at the Mac App Store to download Lion. Save a copy of that installer to your Downloads folder because the installer deletes itself at the end of the installation.
     Lion System Requirements
       1. Mac computer with an Intel Core 2 Duo, Core i3, Core i5, Core i7,
           or Xeon processor
       2. 2GB of memory
       3. OS X v10.6.6 or later (v10.6.8 recommended)
       4. 7GB of available space
       5. Some features require an Apple ID; terms apply.
Upgrading to Mountain Lion
To upgrade to Mountain Lion you must have Snow Leopard 10.6.8 or Lion installed. Purchase and download Mountain Lion from the App Store. Sign in using your Apple ID. Mountain Lion is $19.99 plus tax. The file is quite large, over 4 GBs, so allow some time to download. It would be preferable to use Ethernet because it is nearly four times faster than wireless.
     OS X Mountain Lion — System Requirements
       Macs that can be upgraded to OS X Mountain Lion
         1. iMac (Mid 2007 or newer) — Model Identifier 7,1 or later
         2. MacBook (Late 2008 Aluminum, or Early 2009 or newer) —
             Model Identifier 5,1 or later
         3. MacBook Pro (Mid/Late 2007 or newer) — Model Identifier 3,1 or later
         4. MacBook Air (Late 2008 or newer) — Model Identifier 2,1 or later
         5. Mac mini (Early 2009 or newer) — Model Identifier 3,1 or later
         6. Mac Pro (Early 2008 or newer) — Model Identifier 3,1 or later
         7. Xserve (Early 2009) — Model Identifier 3,1 or later
To find the model identifier open System Profiler in the Utilities folder. It's displayed in the panel on the right.
Are my applications compatible?
         See App Compatibility Table — RoaringApps.
     For a complete How-To introduction from Apple see Upgrade to OS X Mountain Lion.