Making Partititions Safer

I was hoping to set up two different W7 operating systems completely separate from each other but things have not worked out as planned.

Both HDDs are linked to the same motherboard and power supply. Windows boot loader has picked up both operating systems (W7 HP and W7 Ultimate) and added them on the boot loader. The first step I have managed to do is under Change Drive Letter and Paths in Disk Management to remove the other HDD from view but that doesn't really seem sufficient as I can see a path in the Windows Disk Defragmenter.

The only thing I can think of is removing the connecting lead from the HDD on the motherboard that I was thinking of using for testing but this defeats the purpose of what I wanted which is a completely separate setup with one drive for testing and another for secure offline document storage. Please advise on any valid solutions.

Welcome to the forum. The best way would be install free virtual box and run one system as a virtual PC

VirtualBox isn't actually what I am after but thanks for the proposed solution.

I reinstalled both OS' by removing the cable from the HDD to the motherboard for each OS separately while installing therefore preventing Windows Bootloader from activating. This worked to prevent Windows bootloader from activating. The following set up is now as such:

C drive 90GB – Windows 7 Ultimate (for online use)
F drive (other HDD) 80GB – Windows 7 HP (for offline use). Will change version to Ultimate.
System Reserved 100MB

OS selection takes place through the BIOS.

I noticed that Ultimate has Bitlocker. I am wondering if I activate Bitlocker on all partitions will this prevent viruses moving from the online hdd to the offline one? Also I am looking to restrict or completely block access from the C to the F drive and vice versa. I am not too sure how System Reserved operates in terms of security.

How does this work on other Windows operating systems or do I need Windows Server to password protect or restrict access to each drive? When I used to work in an office (many years ago...) I am sure that there were network drives that we were unable to access.

Also does Windows 10 have Bitlocker included in all versions?

Does your BIOS have an option to password your hds some do

I am not taking the BIOS route as it does not solve what I am after.

I have used BitLocker for the first time and encrypted both main partitions in each HDD so neither can view the other. My problem at the moment is with the System Reserved partition. I tried to encrypt it and my pc wouldn't boot so I decrypted it. I am worried about testing this again although BitLocker leaves options to be activated on System Reserved.

I don't know if System Reserved should have BitLocker activated. If not then it is a potential security flaw.