Would you guys recommend a pci slot cooler to cool a 9800 pro?

i will be overclocking this card

Yes it will help

Tho you may want to consider other options as well.
slot fans seem to work best as simple exhaust fans, at bottom of case
venting heat out of case. If this is agp card and you put pci fan just
below it, you could be making the gpu fan/fans work harder.
The pci pulling air away from gpu fans and gpu fan try to blow air onto heatsink.

Heat managment generally consists of:

1. Fresh cool air intake, two locations at front of case
bottom front (120mm) and upper or top of front.

2. Heat extraction, heatsinks and fans, video and cpu fans
tend to blow towards heatsink expelling heat into case viods.

3. Exhaust, fans at rear or top or side panel fans. It's up to you which
direction these fans work and what size (80mm 120mm), side panel
fans tend to work as intakes, supplying air to cpu and video.

4. Power supply, best fan configuration is 120mm on bottom of PSU and
an internal 80mm, both exhausting.

5. HDD fans are ussually in upper large bays and are intake fans. The newer
HDD fans are directly attatched to HDD.

There are many more options some go into the extreme like
emerssing your whole case in pure mineral oil.
Various water/liquid cooling devices.
and aquarium cooling freon based cooling.
G'Luck
BtW
Welcome to TechSpot!

thanks...i need to make it longer...

wait, so is it good for a pci slot cooler to make the gpu work harder? this is an agp. or is it bad that it makes the gpu work harder?...? is that a good thing or bad thing

Depends

Depends on which way the on video board fan/fans
are blowing. I'm not familiar with your 9800.
Most fans have a couple of arrows that show which
direction the blades rotate and what direction it blows.
You may want to try flipping the fans so they blow out
making the the pci fan a help..
G'Luck