Once you are sure that everything is working you can remove the Windows.old folder.
Windows may resist but CCleaner will do it, and eventually Windows will remove it, itself.
For the webcam go to Device Manager, find Imaging Devices and see if it shows the camera there. If so right click on the camera and select Properties...
Go to the Drivers tab and select update drivers and see it that helps.
If all else fails, you can try telling it to remove the camera and reboot, it should detect the camera and set it up automatically.
I usually use this step if I can't find anything else, for almost any Widows component, Sound, internet device and it almost always works.
I don't remember doing it for my camera though and I'm not using a laptop.
As for the space used, look at you Users Folder and see how big that is, my windows installation including the Users Folder is about 25 Gigabytes, add the 20 for the .old file and you already have 45, and you probably have another 15 in odds and ends software.
I don't put any of my software in my C:\ drive and it's still 141 Gigabytes. At one time on a fresh install it was over 60 just because of the size of the Driver Store folder.