First I had to find my Vista disks; as I didn't use them for 6 years, I searched the whole house, including the attics. I found everything, up to the ZX81, my very first computer, from the 80's! Eventually I found the laptop cardboard box in... the kitchen, upon a cupboard, under a long un-used wok. Oooookay.
First reinstallation took a couple of hours and left me with a HD filled to the brim (280Go on 320). Without my personal files yet. That sounded fishy, so I read the instructions of my Dell 'puter (RTFM!!!). I followed them, used their disk to empty the hard disk, make a partition, reinstall Vista... Phew! Only 22Go in use! Victory!
I decided to install only the softwares I really use—you know all what we can add now and then, and that we end never using! Same for the drivers as I was asked for them, and my profiles (Hello Firefox and Thunderbird, good old faithfuls), and just the files I really need all the time. Now I have 100Go in use, and everything's working fine and fast.
I feel like a geek. A tiny one :oD
BTW, I asked Microsoft to add just the compulsory updates. It brought first... 100 of them. And every 2 or 3 days, more. Who says Windows is but a kludge with patches??? Hmm???
NB—Most of the memory seems to be taken by p0m manga (yaoi). Nose bleed and face-desk.