Cleaning up root disk from multiple reinstalls of Windows 7

I'm visiting a friend who has resorted to reinstalling Windows 7 64 bit every time his installation was corrupted by malware. His root drive is filling up with Windows files in multiple directories:
C:\Users - Created 7/14/2009, Modified 2/18/2015
C:\Windows - Created 7/14/2009, Modified 2/19/2015
C:\Windows.old (with its own Users and Windows subfolders) - Created 6/18/2014, Modified 6/17/2014
C:|Windows.old.000 (with its own Users and Windows subfolders) - Created 2/18/2015, Modified 2/19/2015

He also has a RECOVERY Drive with a Windows folder with its System 32 subfolder with 11/9/2009 Date Modified.

Can he safely delete the Windows.old and Windows.old.000 folders without impacting his system?

Any direct advice and/or referral to guidance is appreciated.

How do I remove the Windows.old folder?

I would have recommended him to format (at least) his root partition during the installation, instead of installing over the infected windows installation.

Clean Install Windows 7

Thank you for the two links on recovering space and performing a clean install.

This is not the modern method to reinstall every time. You only need to get one perfect Clean Reinstall Windows 7 then save externally a backup image to reapply in place of reinstall.

Always delete all partitions during the booted reinstall, unless you have Dell and the hardware diagnostics will still run from F12 boot menu, then save the Utility partition only.

Everything needed to get and keep a perfect reinstall is in the blue link, which has been used by over 1.3 million consumers without a single complaint.

In addition, as suggested use MSE for basic AV protection, but if user is regularly infected then what has worked every time is to add Malwarebytes Real Time protection and they never get infected again.

@ gregrocker
The clean reinstall, as you call it , I understand to be an image of your system drive after you did a clean install of windows, 'the way you like it', with all the updates, drivers and some programs already installed. -- In this case he will still have to do a clean install of windows first, before he can even make an image of his partition.
In most cases, i do agree, to install from a clean windows installation medium to avoid the manufacturer's bloatware included on the recovery partition, (like outdated trail versions of Norton, and an office packet that you can use for 30 days) and get fresh drivers from the manufacturer's website --
but for me, and probably a lot more computer enthusiasts , this is where the problems start.
My average computer installation lasts me about a year, in which many things on my computer change.
I swap hardware, install newer versions of drivers and software, change registry settings, discover that some windows updates actually break my computer, ETC. after a few months i usually have to toss my first partition image, because it is totally outdated.
And after about a year, when i notice that my computer is filling with leftovers from programs i tried, registry changes i didn't remember don't work as they should, and some things don't work as they should after i had to fix some virus or malware infection and some of those problems sneaked into my latest backups -- I usually decide it's time to toss all my backups and do a total clean reinstall -- with all the newest drivers, from the new and updated programs, all my newest settings.
Like a springtime cleaning.
(takes me about a week, in which my wife will hate me).
But only then, my computer will be the way i want it to be.

In your tutorial, that is otherwise very good and thorough, i wonder why you don't recommend people to watch their event log for errors, before making a system image??

Each year I attend Global MVP Summit for a week on MS' campus with 1500 MVP's from all over the world. While I'm under Non-Disclosure Agreement for what is discussed there, the past November we had many meetings with the Windows Ten Developers Team that convinced me they are completely open to our input this time around (the exact opposite of Windows 8) and seemed heartily in agreement with Clean Reinstall of factory OEM being fully in MS' interest - since its the only way consumers have the real operating system and not a compromised version of it.

I'm hoping and working for a Clean Reinstall being the default Reset for Windows 10, since it already uses the install.wim of the OS and the other crap is shoveled in afterward. If this isn't what they come up with for Windows 10, then we'll have another cause to draw more millions to the Forums to get the best possible install. We won't know for sure until we see the first factory install of Windows 10.