Don't replace it, just buy another computer.  Use the old one just for your business and financial stuff and do not even put it online.   That is what I did.  I bought a KVM switch and have the old "business" computer under the right side of the desk, the new"internet" computer under the left side of the desk, and one keyboard, video monitor, and mouse running both of them.  Just remember the 3 most important things to do to a computer ...

Backup

Backup

Backup

You don't lose anything, your info is secure, and other than taking up a bit more space it is a win/win situation.  And if your new computer is bundled it will have a new flat screen that takes less space on the desk.