Should I upgrade?

Does the computer have Snow Leopard 10.6.8 or Lion 10.7.5?

If the computer is capable of running Mt Lion 10.8.5, it could run Mavericks 10.9.2.

However it may really need more RAM just to be sure that would not bog it down.

What model build year version iMac 9.1 is it?

Did you get it from the Apple Store online?

There were Four versions in that model number.

Early-2009, Mid-2009, Late-2009: 24", 20" 21.5", 27".

By more thoroughly identifying it, the level

of upgrade or update is better researchable.

Good luck & happy computing! 🙂

edited

tabguy wrote:

I bought a reconditioned imac 9.1.

http://support.apple.com/kb/HT1758How to identify iMac models

Should I update to Mt. Lion?

That is entirely up to you.

what is Maverick?

An OS (operating system). Click on the gray Mac tag at at the top of the website & read all about it. Especially the system requirements.

Should I get that also?

Entirely up to you. It's free.

My wife and I both have macbooks with Mt Lion