Is it possible to decrease the face count dramatically so I can continue working without crashing? I have an issue for the amount of faces I have, I have made a decent looking character with blender (just the head) so far. However, I finally get to the step where I need to add textures and I mark my seams and unwrap, my whole computer freezes and blender crashes. I have ~393, 000 faces.

I would really like to keep my work so far, instead of redoing it for the 4th time, is there any way I could keep my beautiful work of detail and awesomeness but decrease my faces.. but still keep my work, and have it still look good when I render it in Blender Render? 

This is how it happened, I have a little issue with hitting the subdivide button alot, not the one in multi-resolution but the other one. And that's because I love detail.

Here is an image of the issue.. 



I would really like to add hair without the lag too~ :(
Another option is to set the "Display Type" to "wire" (in the "Object" tab) 

Might not be exactly what you want, especially if you're texturing, but thought it would be good to mention it here... I've realized, looking back, that my work would have often been WAY easier if I had remembered the "wire" option, or, even better, the "box" option, on some of my projects... just thought I'd mention that.