If your looking for a good freeware 777 panel - I'd recommend the following:
Regarding the PMDG 747 - check it out here:http://www.precisionmanuals.com/html/products.htm
They really are top notch products from PMDG - I have the 737NG and 800/900 upgrade - highly recommended if you are into a more 'realistic' flight. For example, the 737 flies within a 5% tolerance of the data issued by Boeing - not bad hey!
And their 747 is probably the most highly anticipated add-on for the next year or so. (Closely followed by their MD
-11 which will be released in '05)
As for your computer - it should be okay. I had a AMD 1.3GHz with 512MB RAM and a 64MB GeForce 4 which ran the 737 reasonably well. Be aware that if you have add-on scenery, tons of AI
or your sliders set high - your FPS will suffer. My computer sadly died last night (not as a result of FS
I hope!), so I'm in the market for a new one.
A shiny 64bit P4 3.2GHz should get the ball rolling I think... :P