Dell supports Win 10, 32-bit, on this model. So why can't you upgrade to that OS? You can download the tools and ISO file to install 32-bit Win 10 directly from Microsoft, but unfortunately, the date for free upgrades to Win 10 has passed, so you'll probably have to purchase a license from Microsoft if you upgrade to Win 10.
My machine was sold to me as one that would upgrade when Windows 10 became available.  Tried many times without success.  Have now learned that my 32 bit machine will accept the upgrade as only a 64 bit machine will accept the upgrade.   My tablet works great but I need a machine built for windows 10.  I feel that Dell should  help me find a resolution other than paying for a new machine because of the sales lead-in that my machine would accept the upgrade.  Can anyone offer a resolution?
3845 Venue Pro will not upgrade to Windows 10.