Can you post/attach your config file? The 6600GT might be a tad slow for very shader intensive stuff, but it's still a powerful SM3.0 card. You could also be just be right on the edge of playability depending on what games you're trying to run with your CPU as well.

Shaders vary pretty widely in GPU power consumption. Some of them have given me slowdowns with models a lot newer than your 6600gt... don't expect CRT.D3D.fx to work very well. ;)

fullscreen=false
fulldouble=false
fullresolution=1280x768
windowresolution=original
output=direct3d
autolock=true
sensitivity=100
waitonerror=true
priority=higher,normal
mapperfile=mapper-SVN-Daum.map
pixelshader=CRT.D3D.bright.fx
usescancodes=true
overscan=0

language=
machine=svga_s3
#machine=cga
vmemsize=2
captures=capture
memsize=16

frameskip=0
aspect=false
linewise=false
char9=false
multiscan=false
scaler=2xsai

vsyncmode=off
vsyncrate=75

core=auto
cputype=auto
cycles=auto
cycleup=10
cycledown=20

nosound=false
swapstereo=false
rate=44100
blocksize=1024
prebuffer=20

mpu401=intelligent
mididevice=default
midiconfig=
mt32ReverseStereo=off
mt32DAC=auto
mt32reverb.mode=auto
mt32reverb.time=5
mt32reverb.level=3

sbtype=sb16
sbbase=220
irq=7
dma=1
hdma=5
sbmixer=true
oplmode=auto
oplemu=default
oplrate=44100
hardwarebase=220

gus=false
gusrate=44100
gusbase=240
gusirq=5
gusdma=3
ultradir=C:\ULTRASND

pcspeaker=true
pcrate=44100
tandy=auto
tandyrate=44100
disney=false
ps1audio=off
ps1audiorate=22050

joysticktype=auto
timed=true
autofire=false
swap34=false
buttonwrap=false

glide=true
grport=600
lfb=full
xms=true
ems=true
umb=true
automount=true
keyboardlayout=auto
files=127

ne2000=true
nicbase=300
nicirq=3
macaddr=AC:DE:48:88:99:AA
realnic=list

CRT requires a DX11 card to perform well. It technically doesn't REQUIRE DX11 but i'm just referring to the cards of that class 😀

You should try the "simple" variation of the shader.

ohthanks ! i like tv blur effect with scanlines but them Are not togheter in any filter in dosbox! can i find something patch to' do this?