MSBROWSE setting for XP clients

We have 500+ client PC's running a mix of Win98, W2k,
WinXP with the primary servers running NT4. In the past,
the client PC's were configured so that MSBROWSE was
disabled. I believe only the PDC and BDC were the master
and backup browsers. Recently I did a random search with
nbtstat and noticed numerous client XP-based PC's were
displaying the "..MSBROWSE..". If this implies that
these PC's are acting as master or backup browsers, what
is the impact to the network and to the individual client
PC?