network slow speed and disconects

Start with some basic questions.
Does this only affect certain systems or all systems? Specific applications? Certain times of day? Completely random?
Start with one machine and note its TCP/IP settings, dns servers, and try to see for yourself the problems.
Most issues like this that are random/periodic can be traced to layer 1/2 issues such as bad cabling not up to CAT5 standards, environmental issues, electrical interference, power problems, etc. You might want to get a good CAT5 cable tester/validator
Next is swtichports/hubs. Note which systems are connected to what and how the hubs/switches are connected together. Very often we'll find duplex mismatches on switchports that cause these type problems.
Managed switches are good because you can see error messages. Unmanaged switches and hubs cannot be manually set with speed/duplex so if you find any servers/pcs that try to set anything other than auto, like 100/full, then this is a guaranteed mismatch.

Next is WAN link. Same issues with possible duplex mismatch between router and switch or router and cable modem or whatever is providing wan services. If it's a T1 then we look at error counters on the DSU interface.

Next is dns/WINS name resolution in Microsoft networks. Perform a DNS audit (part of the engineer's toolkit from Solarwinds http://www.solarwinds.net - download a 30 day eval)

Make sure you download Wireshark http://www.wireshark.org  - it's the updated version of Ethereal sniffer

Post back with any specific questions.

i am onsite looking around. The contact is in a class and will be out shgortly. They told someof teh users to tell me that there outlook will disconect, and there crm will becomee extremly slow and sometimes hang nad disconeect. I will checdk the above questions, but what canI check on exchnage and crm?

All the above.. DNS/NetBios name resolution particularly..

i am running the network performance monitor how does it work what shoudl I look for?

Did you find the problems?