Things changed when one can easily get 1TB HDD without burning a hole in pocket.
Most of the time people just skipped the partitioning chores, leaving a whole big hard disk into 1 partition.
As such, they mix system & personal stuffs into a big bowl, and lost both when disaster comes.
In my case, I have 10GB as my system partition since years ago and still practise it without problem.
After switching Firefox to Firefox Portable, from my much space-limited system partition to other much spacious hard disk partition, I managed to recover much space to be utilised, although it's then being consuming by MS updates patches.
Not sooner after installing Google Chrome 4, I wondered what eats up my system partition till 0kb.
I cleared up other temp files, temporary freed up some space, but quickly I faced with the same situation.
After months I spared Google Chrome, finally I decided to switch Google Chrome to Google Chrome Portable.
To my surprise, this frees up >300MB in my poor system partition!
So I would really suggest to Go Green - go Portable, and that the new age programmers would kindly consider much in making of their ever-growing big fat applications, to be much aware of the what they might consumed.
