I've used an MS Excel plugin (xla file w/dll) since the days of Win2k, and it's worked pretty well. It interfaces a data acquisition unit strait into excel, and I find it to be better suited to my needs than Labview, Matlab, etc. However, the new computer came with 64bit Windows 7 (last one was 32bit XP, Office2007). I tried the installer CD, no dice (error about 64bit versions of Windows). I tried it in compatibility mode, also no dice. I tried it on the built in XP virtual machine, that works, but isn't a good permanent solution. I then copied the installed folder (.xla file, couple .dll libraries) to the Win7 install. Load Excel, browse to add the plugin, and it works great. It talks to the box, samples data at 25kHz, does output, etc.
Now for the catch, if I close Excel, when I reload Excel I get an error "daswiz.dll" [my plugin] failed/could not load/something like that, and the plugin isn't there. If I disable the add-in, then re-enable it the problem does not go away. If I move the plugin file to a different directory, such that on load Excel prompts me to remove the add-in from the list, then I put it in again at the new location it works great...until I close Excel.
It seems like this should be a documented issue, but I can't seem to find it. If I don't come up with an answer in the pretty near future I'm just going to send the computer back and get one downgraded to XP. I'm trying to avoid that because I see future XP support as being a bit thin.