What is the current bandwidth utilization on both the 100Mb/s segment and the 10Mb/s segments?  If you are consistently lower than 40% (70% if it is token ring), you probably have little to gain from increasing the bandwidth.

If your 10Mb/s segment(s) are saturated, ie. over 40% utilization,  you can gain network speed by upgrading to 100Mb/s. If that is the case, your next question will be server load.

Monitor the server(s) for existing resource utilization-CPU, memory, storage- for the existing 100Mb/s users, leaving the 10Mb/s segments at that speed for now.  Assuming relatively equal usage by all users, you can forecast what the bandwidth increase effect will be in resource utilization. Then decide whether the increased bandwidth will have a detrimental effect on overall server performance.

Has this already been done?  Is this the designer's basis for the preference to keep the 10Mb/s segments?

So much for the technical.  One last opinion (as is all of the above)- if there is no problem from the users' point of view and you do, indeed, have a high level of respect for the designer, why change it?  Sometimes you can be right and still lose.

This is more of a question really, but if you are connecting 10 base-t switches to a 100 base-t switch, surley the end user will not see much difference as there will be a bottle neck for each user i.e. the 10 base-t switch. Is that right or am a talking complete rubbish!!!

KEv

Well, Kev, that's the dilemna.  I need to change all the outlying switches, hubs and data converters to 10/100--to say nothing for NIC's.  I've already decided, thanks to the feedback from this board and other sources, that I will do the upgrade and then use a programmable switch or VLAN to control the through-put.  In all fairness to the hardware tech who designed the system, it was being used for word processing before I came and I have implemented some more demanding database systems that are being bogged down by the 10mbs.  I had to remove photos from the main screen of the database because it took too long to scroll through the records. Go figure! Any expert opinion on which switches I should go with that will fit the bill?  Right now, all our switches and data converters are Allied Telesyn.