Before you do ANYTHING, make sure you have Service Pack 1 & Service Pack 2 - This will improve performance vastly as well as fix many, many bugs.
Performance Optimisation
Follow these steps to optimize your system for running FSX:
1. Download all patches and updates for your computer (Windows Update)
2. Download and install the latest drivers for your graphics card from ATI or nVidia.
3. Run Disk Cleanup (System Tools) or run CCleaner
4. Defragment your hard drive. Preferably use commercial software to do this, such as Perfect Disk or O&O Defrag which offer a Complete/Name method (this will increase FPS quite a lot). If you don't want to buy these, at least use the defragmentor that is included in windows (XP: Start>All Programs>Accessories>System Tools, Vista: just search for "defragment"). This may take a long time but is very important, so be patient!
5. If you've downloaded and installed CCleaner from step 4, open it, click Tools and then Startup. These are all of the things that open and run when you turn on your computer, slowing things down. Don't simply delete them all as some may be important such as drivers. Search the name on Google to find out about what it does. If you don't need it, then click it and select "Delete". If you dont have CCleaner, then you can do the same thing by typing in "msconfig" in Start>Run.
NOTE: You should have a MAXIMUM of 7 things on here. Most things on this list you DON'T need
6. If you've been using the computer for browsing and other things, restart your computer before you start FSX. This will 'refresh' the RAM.
7. Optimise your sliders! If you're getting low FPS, make these changes to your sliders:
- Set a target frame rate
- Turn off light bloom
- Turn off aircraft casts shadow on itself
- Reduce mesh complexity
- Lower Water effects
- Reduce land and sea traffic density
- Reduce the amount of aviation traffic
- Reduce Autogen density
Every fortnight or so, repeat steps 2-5.
Settings
I've only tried this out recently, but go into the FSX Settings and change the sliders so that performance is smooth in major airports. Then click the Save button and save it as "High density". Do the same for "Mid Density" and "Low Density". Then when you're going to fly in, say, Princess Juliana, load the "Low Density" settings, but when you're going to fly in Heathrow, load "High Density" settings.
Hardware Level
Microsoft's minimum system requirements for FSX are a bit of a laugh in my opinion.
Windows XP SP2 / Windows Vista
Processor: 1.0 Ghz
RAM: Windows XP SP2 - 256MB, Windows Vista – 512MB
Hard Drive: 14GB
Video Card: 32MB DirectX 9 compatible
Other: DX9 hardware compatibility and audio board with speakers and/or headphones
Online/Multiplayer Requirements: 56.6 kbps or better for online play
If you have a PC which meets the minimum system requirements, you should be able to run FSX with every setting Minimal. These are my recommended and best settings. Remember that different types of processors are faster than others, and the amount of GHz can differ in terms of real world speed/performance.
Recommended (If you don't have this, you might as well stay with FS2004)
Windows XP SP3 / Windows Vista SP1
Processor: 2.0 GHz (preferably dual core)
RAM: 1GB (2GB if you have Vista)
Hard Drive: 60GB+
Video Card: DX9+ 256MB Card
256+ Kbps Broadband
Best (You should be able to run FSX pretty much all sliders High/Ultra High depending on exact components)
Windows XP SP3 / Windows Vista SP1
Processor: 3 GHz Dual Core
RAM: 3GB (4GB Vista) 800MHz+
Hard Drive: 160GB+
Video Card: DX9/DX10 512MB Card
512+ Kbps Broadband
Things to note if you're getting a new computer: FSX does NOT make use of SLI/Crossfire. This is because FSX uses much more CPU power than GPU power. Also, FSX is still not fully DX10 compatible, but a patch is on its way.
Components to run FSX Ultra High
Processor
Ideally you'd be looking for a Quad core from the Core 2 range of Intel chips. Then you should overclock it to around 3GHz, even more if you want. If you don't know how to overclock, you could get the higher end of the Quad Core processors. If you don't have as much money to burn, you could get a Core 2 Duo E6600 and overclock it to higher clock speeds in excess of 3GHz. SP1 and SP2 take advantage of multiple cores so you'll benefit from Core 2 Duo's.
RAM
If you don't run many things at the same time as FSX, then 3GB of RAM should be sufficient. Ideally you'll want to get 4GB, but only do this if you have a 64 bit operating system.
Hard Drive
The hard drive won't affect the game too much, unless you have low amounts of RAM. Then your computer will be continually swapping scenery textures. Faster hard drives will lower the time it'll take and make the game load slightly faster. Have a minimum of 60GB though, because if you have much less, chances are it's fuller, and your drive can't be defragmented as well.
Video Card
I'd recommend the nVidia 7950GT 512MB minimum. But any modern, fast and powerful 512MB card should take it, if you have the extra money you could go for a DirectX 10 card.
Internet Connection
This will only affect you if you use FSX Multiplayer. If your internet connection isn't fast enough, things will start to stutter. I'd recommend a 512 Kbps connection. Keep in mind that what your ISP say is different from what it actually is, so you may need an "up to 2 Mbps" line to get 512 Kbps speeds.
What settings will I be able to run FSX?
Because a different selection of components act so differently from another, we cannot say for definate that you'll be able to run FSX Ultra high. Reply to this topic with your System specifications (Find this by right clicking "My Computer" and selecting "Properties") and we will try to estimate and give suggestions.
They are the absolute minimum FSX will run on the lowest setting at all without crashing. Naturally they'd want to keep this as low as possible to more people buy the game.