Efficient System Partition size

I would like to keep my Windows 7 system partition relatively small.
-- it is Windows 7 Home Premium, 64-bit,
--the pagefile.sys file would be to a partition on another disk,
- My "My Documents" would be on another partition.

So the Windows 7 system partition would contain "only" Windows, installed programs, temporary files.

What would be a reasonably small size for this partition? I'm thinking 20-25GB should be plenty. For comparison, the disk space used for the equivalent on my old XP (32-bit) system is 10 GB (about 65,000 files).

Also, with 8GB memory, what size should the PageFile be? 4GB?, 8GB?, 12GB? or …?

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Some PageFile links (there is some disinformation, so be careful):
How to optimise your Windows swap file | News | TechRadar UK
Gaming performance & pagefile windows 7 x64 - config-customize - windows-7
Pagefile Size Windows Vista 64-bit with 8GB RAM - Configuration-Customize - Windows-Vista
Hard drive speed Windows 7 + Page file - Hard-Disks - Storage

Page file settings
https://www.sevenforums.com/general-d...-sys-file.html
No page file should be faster?

With hard drives being incredibly cheap these days, what is the primary incentive to keeping the OS partition as small as possible? I can understand trying to load as little as possible to the machine to really make it run as quickly as possible, but I wouldn't artificially limit myself to being in a really small partition for the OS.

The only real exception would be if you had to stick to a smaller partition because you wanted to use an SSD drive. I'm running an 80GB SSD for my OS and have a 1TB mechanical drive for storage, my page file, etc. With Windows 7 64-bit and keeping my installs fairly small with a game or 2, I'm using about 24GB or disk space on C.

With regards to your page file, with 8GB of RAM, it's not likely to be used much at all. However, I also have 8GB of RAM and I went ahead and just set the page file to 12GB and put it on my 1TB storage drive. Again, disk space is incredibly cheap so I don't even notice the 12GB over there. However, I would have as easily just created a 1GB file....as I don't really think my machine hardly ever touches it.

Thank you for the replies, guys.

Thoughts from anybody-else?

I am asking as I would prefer to get the sizes right in the first place:
-- the disk is a multiboot system disk,
-- I use partitions to organise things to make image backups smaller and faster,
-- some areas of the partitions store unmoveable files,
-- partitions cannot be extended to the left without using a third-party tool,
-- I did read (in "Windows 7 in Depth") that, once shrunk, the OS partition cannot be extended; see here: Extend Boot Volume

Any other comments on the OS partition size? (excluding "My Documents" and the PageFile)