Would I be smart to buy a new computer, or hope I've got everything backed up, and wait and see how long it lives?

Is a computer like a car: maybe we'd better trade old Betsy before we start having trouble with 'er...?

I have a Dell which is about five years old. I've had the power supply and the hard drive replaced. What a hassle. Grrr.

I'm trying to decide whether to get a new one or take my chances. And I have no clue what kind to get. If I switch to Mac, will I even be able to figure out how to use it?

Decisions, decisions. I am so bad at this.