My 4 year old is great. Or was. I have had 6 or 7 computers going back into the 1980's. (Commodore 64/QuantumLink).
I need to find a person that can help me either clean the old or buy a new one. I usually just went into store and bought one. But I find that it either wasn't what I needed or what I really wanted!
  I am disabled. But I take lots of pictures. Before injuries. I played many instruments. Some session work. So I LOVE music. I have Rhapsody and have thousands and thousands of songs on the computer. I GUESS that's a storage issue. (I'm really not 100% on how to do that).
 I have icons filling up my DISPLAY page. Many things that can be deleted. But about 10 YEARS ago an tech told me I could delete a lot of files. These were files that shouldn't have ever been deleted. Compaq sent me all that software that belonged back on the computer and a few other things!
 Because of great leaps in computers every other day. I assume a new tower would be best. If I do that how simple or difficult is it to use BOTH computers on the new one. Or share monitor?
Please send e-mail if possible.
 Sorry but I need many answers. Being disabled makes leaving difficult for me.I don't know if it's just me, but I had a hard time understanding exactly what it is you wanted to do. Your post is kind of all over the place. What do you want to do exactly?

It would be helpful if you could
  Tell us how many computers we're talking about here.
  Tell us the brand and model of the computer(s)
  Tell us which version of windows and service packs you're running on the computer(s).
  Tell us the capacity and free space on the hard drive(s)
  Tell us what virus protection you have.
  Tell us what error messages (if any) you're getting.
  Tell us in detail what it is you're wanting to do exactly

You cannot give too much information about the system. Withholding information seldom solves a problem quickly, if at all.

And remember don't post messages with any personal information such as personal e-mail address, home address, phone number, credit card information, etc. All posts can be viewed by anyone or anything visiting the forums.Also, give some information about your disability without getting too personal. My problem is mostly low vision and plus old age.
What helps me is having two monitors.

As for too many icons, you can create new folders on you desktop and drag  and drop LESS used icons into the folders. I also change the icons for the folders so I can spot them even when the words are not in focus. (Beyond 18 inches my high power eye glasses can not focus.)

Also, VOICE recognition is now part of Windows 7. Not perfect, but it helps. My advice  is no get a refurbished computer with Windows 7 Home Premium. You already have a good monitor, -Right? Refurbished computers with dual core and one TB drive and Windows 7 go for about $250 with a one-year warranty.

IMHO, cutting edge PCs offer little for disabled persons. Any computer that was  very good two or three years ago is still a good deal if it has a warranty.
Here is an Acer on eBay:
Quote

ACER ASPIRE AX1430G-UW30P AMD E-450 1.65GHZ 4GB 1TB DVDRW PC Desktop
Get fast shipping and excellent service when you buy from eBay Top-rated sellers
Returns: Accepted within 14 days
   Buy It Now $249.49
Free Shipping    Time left: 12d