I came across the following post and wanted to see what the issue was since I routinely use Irfanview myself (it is a great, free no strings attached piece of software).

So I contacted the creator of Irfanview directly regarding the error, and he was able to pinpoint the exact nature of the problem.  As it turns out, the ico files created by Irfanview are just fine.  The issue is that MS Access would seem to expect a specific type of ico file (and doesn’t tell anyone this).

Irfanview creates a 24BPP (with no alpha layer) ico file while MS Access seems (based on my testing and returned information from Irfan) to expect a 32BPP with an alpha layer ico file.

So for anyone else ever seeing this this of error.  An ico is not an ico in the world of MS Access.  It is picky and requires a specific type of ico file.  So just be sure of the type of file your are creating is a 32BPP with an alpha layer ico and you should have no problems using them as a picture for a button.  Alternately, instead of having such issues using a ico file, use BMPs instead.  I personally don’t like BMPs as they aren’t used in any other programming (always jpg, gif, png, ico) so I will stay with ico so I can reuse them easily where I please.  It would be nice if MS would integrate common image files into the application, but that is out of my hands (if it were up to me many issues like this would have been resolve a long time ago!).

Hopefully this will help someone out.