New server preformance crawling

You may want to ck out this article, which I always reference on my SBS installs:

Performance Tuning Guidelines for Windows Server 2003

http://www.microsoft.com/windowsserver2003/evaluation/performance/tuning.mspx

Also, did you defrag your hard drives after the installation?  If not, do so.  

havnt defraged but will tonight but would that really stop clients connection to exchange?? or just slow down?

I think my head was fixated on Performance, but after re-reading your question, it seems to be a networking issue that is causing this behavior.  Is this a multihomed system?  To decrease the possibilities, if it were me, I would plug a laptop into one of the NICs directly and try testing from there.  Then move to your switch / router until the problem presents itself again.  

think its got to be with the server.....prob a setting im overlooking the change happened when i changed out from old box to new one this weekend

If they are having problems connecting, I would look at DNS possibly, but if they are being disconnected once they authenticate, that is an entirely different issue.

some more info that may help out getting the rest of the story from the end users now....
they have 2 server based apps and exchange running on server all of which at intermediate time loose connection or give network errors but after relogging they are able to get back on app. outlook however give them cant connect to server errors still .  I have put outlook in cashed mode on all clients to just give me some time to work on problem

looked at dns on server and clients and they both look correct.  yes they loose connection after they auth which is baffeling me.

server nic's look to itself for dns and to firewall for gateway
in dns propertys listen is set to both server nic's and foward are looking at isp dns

clients nic's are looking at server for dns and firewall for gateway

reading all this tonight but will not have a down time to do much work untill tomarow night
thankx for all the material so far

Thankx for all the info Fatal found my prob was someone changed a printer ip without informing me and had a ip conflict going on (some users are a PAIN!) once that was corrected its been running smooth since.
Thankx again for the info on tweaking and your quick response to help a fellow in need.

Ha...  >>some users are a PAIN<<  Isn't that the truth..!!    And conflicting IP addresses will surely throw a wrench into the mix..   You know, I should have thought of that, but as we are both admins, this is something that is many times overlooked..  We just assume that no one would do something like this without letting us know about it beforehand..  :)

Glad you found it, and thanks a bunch..!!

FE