Windows XP pro problems with File and printer sharing

I support a company network with several machines,
including about a dozen windows 2000 machines, a windows
2000 domain controller and 2 windows xp pro based
laptops. One of the laptops recently started slowing
down. Sending or retrieving files from any of the
machines on the network become slower and slower and
eventually just intermitent. If I run a repair on the
connection it seems to work fine for about thrity seconds
and then it dies again. It does this whether or not it is
authenticating on the network or logging in locally.
Also, once every few minutes it will decide to work fine
for about thirty seconds and then die again. Where he is
working on several GB files this is rather annoying.

Also, the other laptop, that is the only other machine
that is running XP will disconnect from the network after
about half an hour of inactivity. The screen savers are
disabled and all power save functions have been turned off
but to no avail. It still detects that the cable is there
and will conect to the internet, however it will not see
any of the windows machines.

A note on the controller: It is not doing anything
complicated. There are no excess policies on it, it is
really just running for basic file control between all the
machines. Other than the fact that it is doing the
authentication and managing the files it isn't doing
anything else. I really wish I could just disable all the
excess AD stuff and run it as a basic controller...

Further information available upon request and any
reasonable suggestions appreciated.

Sean Davis