Where to install games will make them operating better, in the system disk (usually drive C) or other drive (D, E, F, ...)? And why?

It still remains that not installing games to the default location is less likely to cause problems than installing to the default location - Program Files (X86).

There is no difference in actual gaming performance, only potential issues outlined above.

It then becomes a matter of balance - how much space to devote to the system and non-gaming stuff,  and how much to your games.

Oh sorry, my fault, but i have only one 500GB HDD running at 7200RPM, i devided it into 2 partitions, 1 for System OS, and one for other stuff!

I have never installed games on the C:\ drive.

With XP it was mostly for organisational purposes. I started using a separate partition for my games ( I also have a dedicated HDD for games now) to make the games folders easy to find  when I wanted to troubleshoot, tweak  .cfg files, and install mods, but with Vista and Win7 comes  a new reason - permissions.

While you can install games selecting  the  'run as administrator' to overcome permissions  issues - why bother ? Just be done with it and install to another Partition or HDD. Even a folder in the C:\ drive is better than using the default location - Program Files (X86).

However, the default location should be used for AV, browsers, and other software that integrates closely with Windows.

btw - The  C:\  drive letter should also be used for Windows, if only for my one example - recent Nvidia drivers default to C:\ when they unpack from the uninstaller, so having Windows with a different driver letter can cause confusion (so I've read on other forums recently).

Second - some games will not run properly when installed to - Program Files (x86), or may not install at all.

While I cannot say how many games will have issues, I have experimented from time to time and one of games that I recall having issues with was Doom 3. Trying to install Doom 3 to the default location (several attempts) crashed my machine, but I had no problem installing to my game HDD . Didn't even use Compatibility mode, which I will add I have only used on a handful of occasions and then only as a precaution. This is with over 100 games installed.

If you do any modding this again avoids permissions issues with some games.

I have only started using an SSD for my OS in the past couple of weeks, but SSD's being small (unless you are wealthy and can run a 500GB drive) I have only left a 20+GB partition for a game or three. I have yet to experiment with this, but will be trying a game that has notorious loading times (Pure) to see if it will speed up the loading. I'm not sure it will as it may be a problem with the game being a port from gaming consoles.

'Green' HDD's should not be used for anything other than storage as they are the slowest @ around 5400rpm.

HDD's  that runs at 7200rpm are fine for games, taking only a few seconds longer to load a level than an SSD, but apparently there are a number of BF3 players who use an SSD for their game.

As as side line - A lot of people have stopped using the Page File (Virtual Memory) because they think they don't need it because they have so much RAM. Obviously this seems to work for them, but some games use the Page File, so you really should keep one. I have a small one with 512MB min and max on my SSD, but keep a larger PF on the game HDD - around 2GB min and max - If you use a custom size and make the min and max the same the PF manages itself better (stays in one block on platter HDD) then when letting Windows use a variable size.

A lot of people argue that an SSD should not have a PF because of extra writes theoretically wearing out the SSD. There is much debate on this subject, but I tend toward the argument that by the time my SSD wears out form doing many writes I will be upgrading to a 'modern' SSD anyway (3-5 yrs, same as HDD ? ).

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It depends on which drive is faster.  Need you system specs and HD info to tell.