Just about any machine you buy today will come with W7.
If you have some XP apps or Dos apps you might find yourself with a headache.
Yes there is compatibility mode.......you can give it a shot.
I am going to replace a Dell Dimension 8300 desktop that is about 8 years old and served me well but has gotten very slow over the years as I am maxing out on memory. I own a small accounting firm and use it solely for accounting and tax applications, word and excel. I also use a DOS based accounting application. Many financial applications still run in Windows XP and will not run above Internet Explorer 8. Graphics are not that important. What is a good basic workhorse desktop? I was looking at the Dell Vostro or Optiplex.