I have been playing Fallout 3 for a while now but now I find that I seem to walk /run at a speed that is as if I'm overburdened or something. I tried getting rid of everything health etc is fine but no difference. Is there a keystroke or setting that will increase run speed above a crawl or is this a software bug. Run speed used to be fine or have I done something stupid

Are your legs crippled ?
Or maybe you've taken a chem and/or gotten so much Rads that reduces your AGL

Do you mean FO3?

Anyway maybe you have taken some chems or have radiation poisoning. I think agility and endurance manage speed so make them high. Check your character screen to see if you have any chem withdrawal or poisoning, or possibly your legs are cripled.

Try hitting Caps Lock. I occasionally inadvertently do this when I think I"m pressing shift to crouch.

Its not that hes crippled or anything, just the run speed is stupidly slow in New Vegas, FO3's cripple run speed is faster than the normal run speed in NV, its pathetic.

Sprint mod.

Yes. This.