need advice on installing files on wd passport drive

You can install the games on either drive.  When you install there should be an option on where to install the game and that is where you select the external drive (whatever drive letter it is) and the folder you want the game to install in.  You could create a folder on the external drive named "Games" and then install all the games in that folder. 

However, installing games in an external USB connected drive will tend to slow down the game and for that reason it's not really a good idea to install them on an external USB drive.

I assume you have a Dimension E310 and it has space for two internal SATA hard drives.  You would be much better off installing a second SATA hard drive, which would be "internal" and will run at the same speed as the existing hard drive.  This won't slow down and cause gaming problems.  An external drive should only be used for storing user data, or used for backing up the internal hard drive.    There should be a plastic hard drive carrier in the second slot and an existing power connection for a second hard drive.  You will need a SATA data cable for the second drive.  HERE is the info from the Dell manual.

I need help on why and how to fix why my Dell 8400 can't recognize the USB connection for a WD Passport 320GB as well as the USB cable for my Blackberry Storm.  I had no trouble (automatic recognition) with 'My Passport' the end of Jan with my new Acer Netbook, but the Dell will not recognize the harddrive even though I already had been using a 1TB WD 'My Book' on the Dell for over the past year.  I've started to download some updates to my Dell, but I don't see anything special pertaining to USB drivers.  With my past calling the Dell Help Center, I always get someone that can't speak English very well.  Thanks.