hi there...

yesterday i suddenly had a massive drop in fps. i usually get about 300+ though now i cant see to get past 60 (its fairly stable though).

i tried alot of advice from google, forums etc but i cant see to fix it.
i've turned on/off vsync, multicore rendering, updated my drivers, used older drivers.

specs - intel core i7 920
nvidia gtx 285
6 gb gtr3
1 tb hd

any help at all would be appreciated.

tried viewing integrity? turn off vsync if you care about performance, not to sure on multicore rendering.

ive tried most in game settings, including vsync.
it doesnt help.

my computer can handle the game on highest settings, as it has for the past 6 months or so.
im confused as to how this has happened all of a sudden... hoping its not a problem with the hardware.

background apps can chew up your memory or be using hard drive.
check resource monitor if you have win7. its in performance tab of task manager.
when I get drop in fps, I usually kill some progs and it fixes it, otherwise could be a server problem/rate settings.

Turn your graphics down for 1, left for dead is not a highly demanding graphics game man, so on medium will be fine.
Turn v-sync to "off" not "application controlled" that will give up a bit of smoothness but it leaches massive fps to have it on.
Also, monitor refresh rates, turn them up.. max
change your resolution if you can.. max it as well if ure not too worried about small print and titles etc.
maybe format your HDD, run steam and l4d off a completely separate one

Given none of that helps, CPU issues can be a lot of the cause.. maybe its running too hot? maybe the video card is getting a bit tired, that is what happened to me when my cpu was running at 60+ degrees and my vid card was getting on a bit.