Installed the new release and virtual box. Perhaps that was the mistake. BOINC cannot access Programs/BOINC and neither can I now. Cannot reinstall the old release, so all projects are dead.

There is not really enough information to go on. So please, explain further. If need be, take a look at this thread for what we may need.

I would really like to know what you set as data directory.
And did you reboot after installing this BOINC + virtual box?
Why can't you reinstall an older release, if there are error messages, what are they?

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The \Program Files\BOINC folder is "inacessible" in explorer or a DOS box. The uninstall went fine, but the install hit a snag.
Rerunning. The options have the data assigned to c:\ProgramData\BOINC which does not exist.
Error 1303. The installer has insufficient privileges to access the directory C:\Program Files\BOINC. The installation cannot continue. Log on as an administrator or contact your system administrator.

There is no other account. This is the first upgrade with a problem. Perhaps a problem crept up in the folder. I'm surprised the uninstall worked. At this point I'll try a reboot, maybe some process has it locked. I suspended (under Activity) so who knows? I don't see the tasks however.

Rebooting allowed the install to proceed. I've never seen an install fail after a successful uninstall. Another experience in thirty+ years :)
Thanks

... c:\ProgramData\BOINC which does not exist.

Well, it does exist, it's just that this is a hidden directory. Windows hides C:\Programdata\ by default. You can then either set "Show hidden files and folders", but it's easier to just add the path to Windows Explorer and instruct it to go there. It will.

Error 1303. The installer has insufficient privileges to access the directory C:\Program Files\BOINC. The installation cannot continue. Log on as an administrator or contact your system administrator.

Do know, that this is a Windows Installer error, not something that BOINC throws as an error. The Windows Installer (or *.MSI file) needs either read and write permissions for the programs directory through the SYSTEM group, or through the Everyone group. That it can't do it at some point could be due to another process taking up those permissions at that time.

So then a reboot will fix that, as you've done.

Apropos,

There is no other account.

There's always the system administrator account. The account that you see UAC pop-ups for when certain intrusive actions need to be taken, and the one that is used when you instruct Windows to run something "as administrator". That'll be another administrator than you.

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