Application Performance Advice Please?

Hello all,

I've been recruited to assist in diagnosing and fixing a performance problem
on an application we have running on SQL Server 7.
The application itself is third party software, so we can't get at the
source code. It's a Client Management system, where consultants all over
the
country track their client meetings, results, action plans, etc. , and has
apparently been problematic for a long time now. I came into this
investigation
in mid-stream, but here's the situation as I understand it:

We have users reporting it's slow, with no discernable pattern with respect
to what part of the application they're using or now particular time of day.
I am told that it doesn't appear to be a bandwith or computer resource
problem. They apparently added two app servers a year or so ago, which
temporarily
improved the performance. We're using a nominal percentage of CPU and
memory.

There are three large tables (approx 8 million rows) that are queried often,
as users click to see their calendar of appointments or review past meetings
with a client, etc. The activity on these tables is over 90% reads
(SELECTS) with about 10% INSERTS/UPDATES. We have attempted to run the Index
Analyzer Wizard twice
but so far it just seems to hang (it could be that the workload file is too
big?) . So, what we're doing now is isolating the SELECT statements that
take a long time to run and manually comparing them to the indexes that
exist on these large tables. Since we can't alter the SQL source code,
we're trying to alter the indexes to improve performance.

What I would like to know is, is there a good way to get benchmark
measurements so we can explicitly measure any performance changes? Also, do
you think
we're going about this the right way, or is there some other avenue we could
be looking at to improve performance?

I recognize that performance questions are tricky to post/answer in a
newsgroup, because usually you need more information than is provided. The
problem is
that this is a high profile investigation (they're hauling us into meetings
every two days to report our progress) and I need to be able to convincingly
state that we have either improved performance by X% , or that it is the
application itself that's the problem and we're stuck with it.

Any thoughts would be deeply appreciated.

Thanks and best regards,

Steve