It may be trying to upgrade you to Win 8 64 bit, you would need 32 bit Win 8. You won't be able to upgrade to 7 as it isn't available to buy from Microsoft any more, only Win 8.1 is.
If you have already bought it, try a clean install.
http://technet.microsoft.com/en-us/library/jj203353.aspx#editions
This should help you out with any luck. Happy upgrading!