<p>We have a few developers working on the same VS2005 solution, but our source control is very bad.  (Our company uses Harvest, which we give a vote of no confidence).</p>

<p>Right now, we're all just working off of the files on a shared lan drive.  Obviously, this causes some problems. But we think it's better than working locally, and tracking the files we touched in a spreadsheet and merging everything manually.  Does anybody have a strategy for merging our changes?</p>

<p>Some of the problems exist because of corporate beaurocracy (like mandating Harvest).  Those same policies prevent introducing new tools into our environment.  So, strategies that avoid buying/downloading new software would work best for us.</p>

Treat the share as if it were your source control system. Make the share read-only, which will force developers to get local copies in order to make changes. You then have a somewhat stable version to compare against. This would help facilitate being able to do "merges". "Checking" code in would have to consist of some sort of backup strategy for the file (possibly making a copy of the file with a timestamp and username as part of the new file name) and replacing the original with the new version.
That being said, doing this type of activity without a real source control system that is reliable is going to be difficult and error-prone.