All PC flight sims have their quirks. All of them also have unofficial community fan updates/mods that greatly improve and expand their features. Some of them are now obscure and difficult to find. It's probably best to decide on one and then ask specifically what you need to do to get it running at its best.
For WW2 flight sims I recommend in order of preference with common concerns:
European Air War
(Works best with NVIDIA FX series or older graphics cards.)
Jane's WW2 Fighters
(No dynamic campaign.)
B17 II - The Mighty Eighth
(A bit obscure nowadays. May have a bit of a learning curve.)
IL-2 Sturmovik
(No dynamic campaign, but unofficial options exist.)
(High learning curve at max realism, but it can be turned down.)
Crimson Skies
(Not realistic at all, but still fun.)
Airfix Dogfighter
(Maybe too silly for you to consider.)
Rowan's Battle of Britain and/or Battle of Britain II
(Ridiculously high levels of realism and stratospheric learning curve.)
Honorable mentions:
1942: The Pacific Air War
(Steam has it, but I'm waiting for a GOG release.)
Red Baron II 3D
(WW1 sim.)
(Hard to choose which of the many excellent unofficial mods to run. They're all great!)
(I recommend Full Canvas Jacket. An oldie, but still a goody!)
Rowan's MiG Alley
(Korean War sim.)
(Very obscure nowadays. Unofficial update may be hard to find.)
(Dynamic campaign can be glitchy, but it's fantastic.)
For a really obscure retro flight sim experience:
Rowan's Air Power.
(Totally ridiculous concept.)
(Totally ridiculous aircraft.)
(Totally fun!)
(Fantastic dynamic campaign with strategy elements.)
(Graphics look like crap unless you can get SVGA mode working.)
(Think of it as a predecessor to Crimson Skies.)
(This game is what got me interested in classical music.)