Windows 7 - Reformat?

Hi, I just upgraded from Win 7 RC (Ultimate) to Win 7 Home Premium on a machine that originally came with Vista. I thought I had done a clean install, but I noticed there is only 16GB free on 70 GB C:drive. (D: drive is 70 GB also, and mostly free). Can that be right? A clean install shouldn't use 54GB should it? Thing is, I can't figure out where all that data is on C:, Windows.old file is only 1.5GB. and I see no trace of any other old files. I guess I must have missed a step and not reformated the HD. I think my mistake was just inserting the disk while the machine was running instead of booting up from disk (?).

1. Can I go back and reinstall, except this time reformat?
2. Do I really need a big empty 70GB D:drive partition, or should I just make it all one big C:drive?

Problem is, it's running PERFECT, and I don't want to screw that up!.......OK, just inserted disk and rebooted, it did not enter setup, just went to my normal Windows 7 Home Premium sign in screen. Maybe I need to change boot order in Bios? I do have an external HD (I disconnected it before install) I could save my Windows.old folder to, if I wanted to keep that data.

Welcome to the Windows 7 Forums! digau

On any premade system you automatically start off with less drive space available due to the hidden OEM recovery partition taking up some 5-10gb of drive space there. Then you have to recalculate drive space according to how they are sold(decimal units of measurement) compared how any OS reads drives(binary units of measurement).

A 70gb(labeled size) drive for example would see some 65.19gb(actual size) of space available before partitioning, formatting, and OSing the drive. When you restarted the machince to boot from the 7 dvd you forgot to change the boot order in the bios if the board lacks a boot device menu key like F4, F11, or another designated F key for selecting the drive or device to boot from. The default boot from the hard drive simply took over.

On a drive that small generally one single primary is all that is seen. Backing up all data and wiping the drive entirely to create one large C primary would be the first step taken before any newer version goes on like 7. If you don't need much drive space for a web browsing machine and nothing else 7 is already on and running. To be more thorough and free up more drive space then nuking the existing partitions for the one new primary would see that tended to.

Run WinDirStat - that will show you exactly what files are on the disk. Then run vssadmin list shadowstorage in elevated Command Prompt. That will show you the size of your shadowstorage where the restore points are stored. Look for the allocated number. And then what Night Hawk says - binary is always 7% less than decimal.

Correct.

Yep, you can.

I just use one, others may beg to differ.

You do yes, to boot from CD/DVD first, save and restart, then hit any key when it prompts you to, and install from there.