it isnt mentioned in the getting started video because that is the default setting for that option

you likely changed the setting accidentally - but no biggie - it is fixed now

as for giving up - no - i think that most people learn the limitations and quirks of the tools and engine, and work comfortably within those.

ive said it before, but i will say it again - working with any radiant editor is 99% frustration and 1% frustration

lol

it actually isn't that bad - but if you take the time to learn how to use the tools properly in the beginning - then it is way easier to make something with them

don't give up, you have all of us to help you along your way

I have been working with some form of Radiant for years and still find it frustrating some times. The map I am working on now had many patches in it. Most of them were at angles. I should have known better. Many hours wasted. The more complicated you try to make a map the more frustrating it can become. The more complicated you make a map the more errors you see.
I am on dialup and cannot play online so I only have one install of cod2. But, during the install you can direct it to another location as you can with most any program installation. Although I have seen some programs require Program Files in their path be it C:, D:, E: etc.

Last night I was about scrap my project and say to hell with it. Today I am back at it. A glutton for punishment. hehe

.NET is a must nowadays. And there are I beleive Service Packs and Hotfixes for .NET. In a standard production environment we run .NET 1.1 and 2.0 with related patches.

As Stryder stated don't give up. You will find that the more you use Radiant or any map editor that it will become easier as you progress.

While working I have at least 8 working versions of the project. Most of them at different stages. As the project gets further along with no errors I will save it over all the rest of the backups so they are all current. And you never know when the old harddrive will crash so back up to CD or another H/D occasionally.
Don't worry about backing up the BSP. You want to backup the .MAP which is in the map_source folder. BSP's are the compiled version which you can't open in the editor.