Some questions about how to improve network speed

Hi. I'm experience some troubles regarding my network speed and I to expose
some questions and I would like your feedback.

1 - I've got a IBM series server quite old from 2002 running W2k server. I'm
thinking to insert a 1GB network card. If connect to 1GB switch and PCs with
1GB network cards the network is supposed to work faster or Windows 2000
cannot run work that fast in network?

2 - My main switchs are Cisco Catalyst 2900 and 2950 of 10/100mbps. I bought
a 1 GB 3com switch, it's quite simple. The model is: 3com baseline switch
2824.

My question is, if I only use a switch to connect PCs what' switch is
supposed to be faster? The 1GB 3com because it can work with that speed or
the cisco even working 10/100mbps because is a superspecial switch and it may
management the network or something??

3 – If I install 1 GB 3com switch should I install cables with Cat6 or Cat5e
is also good to work with 1GB?

4 – What do you recommend me to make my network run faster? Don’t forget
I’ve got 1.5GB of ram, raid 5, 1gb processor and w2k server w/ sp4.


Thanks,
Marco