Questions about partitions & multiple instances of Windows 7 Ultimate

He everyone, long time lurker, first time I've actually had the need to post.

I've been reading and searching for a few days, but there are still some things I'm unclear on so I'm hoping some of you may have some advice/answers/suggestions.

I'm in the process of reconfiguring my laptop; I have a new 500gb drive that I will be splitting into two partitions, and then installing a copy of Win 7 64x on each.

One is basically my personal files and work files from my own business, and the other is for a new company that I will be working for.

Since you may ask, the reason I'm doing it this way vs a VM etc, is that the new company already runs all of their stuff inside of a VM, and I don't want to run a VM inside a VM (if that's even possible), and I want/need to keep everything as separate and as clean as possible.

All of this will be new/fresh installs, no upgrades, brand new hard drive, etc.

So with all that said, my questions are:

1) Is there any downside to not having the 100mb "system" partition that Win 7 tries to force on you ?

It's not a huge deal but it just annoys me. I've read plenty on how to keep it from creating it, but I can't seem to find a definitive answer on whether there are any negative repercussions from NOT having it there. The only thing I've found was related to the Bitlocker encryption etc, but I'm not / will not ever be using that.

2) Once I have both copies installed on their respective partitions, will they be able to see each other or no ?

For example, say partition/win copy 1 is "personal", and partition/win copy 2 is "work". When I am booted up into "personal", will the other partition show up/be accessible as drive D:\ or something, or will it just be ignored as if it's not even there ?

Basically what I don't understand is, after they are both installed, when I boot into each, will each one have it's own "C:" drive etc, or will copy 1 always be C: and copy 2 always be D: ?

I realize that may be a bit of a dumb question but I haven't installed multiple OS's before so I don't entirely understand how it works.

Anyhow, thanks in advance for any answers/comments you may have.

You don't need the 100mb SysReserved partition and can avoid it by pre-partitioning using free Partition Wizard bootable CD. However it's actually good to have in a Dual Boot so that wiping the first installed OS doesn't take the boot files for both with it. So I would just do a booted clean install deleting all and then creating my partitions using Custom drive options as shown here: Clean Install Windows 7

You'll see the other partition in Explorer and can access your files, even link them to related Library so they're handy and don't need copying over: Library - Include a Folder - Windows 7 Forums

Just remember to do both from booted installer so that Win7 correctly sees itself as C when each is booted.

You might find this tutorial handy, which explains how to edit your boot menu:

Dual Boot - Change OS Name in Windows Boot Manager

For example, you could name your respective systems as Windows Personal and Windows Work - the choice is yours.

Whichever system you boot into it will take the drive letter C, with the other one taking the first available drive letter, typically D.