W7x64 SP1 PRO OS size/footprint is huge (hidden files/data)

As the title says.

I'm a fairly advanced computer/hardware user. Advanced enough to get myself into a whole lot of trouble if I'm not careful LOL. This is a first for me. I'm trying to build a quad-boot machine (don't ask) (W8.1/XP - HDD-0 & W7/CentOS HDD-2) Putting 8.1 & XP on HDD-0 was easy enough and straight forward.

I then threw an old 80gb WD raptor drive in and put W7x64 SP1 on it yesterday. Did my updates, etc. I assumed that the 80GB drive could be partitioned down to 2x 40GB and I could throw CentOS on the Partition2 of HDD2 easily... Except when I went into W7 this morning (Computer Management) to shrink down the volume I'm seeing something funky.

When I go to folder options and "view hidden folders and files" then open up C drive and Ctrl+A, Right click and choose properties I get:



and






So what's going on... or what am I missing???

I know the easy solution would be to format the drive, partition first and then install W7 and CentOS onto each partition - but I am curious and can't let this go...

Thanks for any help - I just want to find where and what the data is on the drive that's hidden somewhere. It's just the bare OS, I've gone into Add/Remove Windows Components and removed pretty much everything I can that I don't need so it would be a very stripped down bare OS...

Thanks

UPDATE:

It did it again...

From the Microsoft website - System Requirements:

Windows 7 system requirements - Microsoft Windows

•16 GB available hard disk space (32-bit) or 20 GB (64-bit)

I formatted the whole 80gb (74 usable) drive into two 37.2GB partitions. I installed W7x64 onto the 37.2GB partition and it's now showing 455mb free and 36.8GB used - I've never paid attention to this before however I do a bunch of VM deployments on 16, 24 or 32GB HDD's and have never had this issue before.

All I want to know is where the hidden files are so I can clean them out.

Thanks for any help.

AddRAM said:

How much memory is installed in this pc ?

Are you deleting or formatting the install partition before you start ?

32gb RAM. It's a development/test box... Yes I am deleting partitions AND formatting the drives. I even went so far as to get the Western Digital tool and zero-write the drive and the same thing happened. W7x64 was taking up about 36.5 GB of space upon initial install.

Well long story short I'm still curious but I got totally fed up with it and I threw in a pile of old 60gb SSD's so I could have a dedicated drive per OS...

I have no clue what it is/was. I'll see if I can duplicate it with the Dell OEM flavor of W7 media vs. the MSFT media.