I've just downloaded 5.2.5 (from 4.43) tride to tun the ,pkg, I get to the stage where I fhave to choose a voloume and they are all unavailible, the startup disc says "You cannot install this software on this volume. (null)" allother discs say "You cannot install this software on this volume. (you must install on the startup volume)" if I disconect all other discs still have the "You cannot install this software on this volume. (null)" message - I'm close to giving this whole thing up it was fine b4 we went to BOINC since then don't know why I bother!
Twin 2Ghz G5 running 10.3.9

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I had the same problem.
Tom B pointed out that the ReadMe.rtf file has the following line (right near the top of the file):

Troubleshooting tip: The installer writes a file /Library/Receipts/BOINC.pkg. If the installer refuses to let you install, trash this file and try again.

After I deleted the file, the instalation proceeded with no further problems.

I had the same problem.
Tom B pointed out that the ReadMe.rtf file has the following line (right near the top of the file):

Troubleshooting tip: The installer writes a file /Library/Receipts/BOINC.pkg. If the installer refuses to let you install, trash this file and try again.

After I deleted the file, the instalation proceeded with no further problems.

Thanks I had read that but couldn't find the file in the reciepts folder, but after your reply looked more into it and realised that I was looking in the library for my account (I have a number of accounts on my computer) and not in the library folder in the HD and lo and behold there it was and all now works, I hope this helps any other multiple account mac owners!
Thanks again James

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