I use a 24 inch screen Mac computer for all my video editing, music composing, and everything else.  Now with everything in beautiful HD, space is tough to keep.  I keep throwing finished older projects onto external hard drives but then they seem buried.  Yesterday as a favor for a friend I made a video tour of her house for sale to put on youtube. I had no space left to do it without deleting a bunch of stuff.  I guess I'm a computer hoarder and don't like to get rid of anything. The mac is wonderful, but with all the stuff I do, should I really have the professional Mac Pro.  I hesitate because first it's expensive, second, the programs are more complicated, third, I'm not in business making money on any of this stuff, forth, I heard that Apple has not upgraded this equipment in a few years since mostly professional studios use it and their focus has been on the things teen agers buy like iphones. I still have stuff on reel to reel tape to convert, and tons of VHS stuff.  Any thoughts

[certified refurbished computers]

Sounds like your external drives are your best options. They do have 1TB and 2TB size external drives now.
This is where I buy of my computer stuff now. I talked with a rep there and he said certified refurbished computers are primarily items that were opened by customers from stores like Walmart,etc. but never taken out of the box. The store is not allowed to re-tape the box. Refurbished are fixed computers that have been used but restored to manufacture specs.

http://www.tigerdirect.com/applications/category/category_tlc.asp?CatId=136&cm_sp=Masthead-_-Computer%20Parts-_-Spot%2036

I would say external hard drives are you best bet. I know that is the route I've gone. Pretty easy really since at least on  PC you can plug them right in via USB and away you go. Simply upgrading to a new PC is not going to fix that fact that you are going to continue to need more space.

The other alternative would be to use a service that gives you disk space on large servers i.e. the cloud. There are really simple easy services like http://dropbox.com and there are more advanced services like http://vps.net/ and https://www.amazon.com/gp/feature.html/ref=amb_link_362776742_2?ie=UTF8&nav_sdd=aps&docId=1000796931&pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-A5&pf_rd_r=0FQJ4EBD2JJ3A8AN0NGA&pf_rd_t=101&pf_rd_p=1364264882&pf_rd_i=507846 The advantage of storing your data on a cloud is that most services allow you to continually upgrade the amount of space you need as you go along yet all your data is kind of all in one place. The thing is in the long run this may cost more since you continue to have monthly payments.  BTW: Starting accounts at Drop Box are free so if you want to test out this concept that may be the way to go at least to see if you like it.

thanks, all good advice. i'll check into dropbox.