I would have thought that if you are mainly interested in spending time in the "Learning Zone", and teaching yourself the ins and outs of all aspects of "Flying", using the Default Cessna 172 Trainer, etc, and your existing Hardware is perfect for running your existing FS 2004 successfully....
...then FS 2004 should fit the bill admirably....without too much stress on either you or the Hardware!...

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I spend most days training, and perfecting my flying skills, in FS 2004 with no problems!... [smiley=thumbsup.gif]...!
Paul...G-BPLF...FS 2004....(and FSX)... 8-)...!
Clocking up the hours in flight training, and perfecting your skills day by day, is the way to go..

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Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.