Wow. The G-Man looks real. Freaky. Eat that Doom 3.
I'd like to share a...revelation I had, during my time here. It came to me when I tried to...classify your species. I realized that you're not actually mammals. Every mammal on this planet instinctively develops a natural equilibrium with the surrounding environment but...you humans do not. You move to an area...and you multiply...until every natural resource is consumed. The only way you can survive is to... spread to another area. There is another organism on this planet that follows the same pattern. Do you know what it is?
A virus. Humans beings are a disease, a cancer of this planet...and we...are the cure.
You can put your saves onto a USB drive, or an XBox 360 memory card, or I've heard that you can also hook up an external USB hard drive too. Plenty of options for keeping saves, though I don't know about downloaded content.