Looking forward to the new features in Windows 8 ? Taking a flying leap but make you flinch at first. If you have no Upgrade Apps option chances are you are Installing the Windows 8.1 Enterprise media which doesn’t support upgrade apps – try the Professional edition media instead. If you are chasing the Hyper V host this is available in both Professional and Enterprise but otherwise you will notice Professional doesn’t get a handful of “Enterprisey” things. Get along to the Features v Editions page to see what you are missing between Enterprise and Professional http://www.microsoft.com/en-us/windows/enterprise/products-and-technologies/windows-8-1/compare/default.aspx.
Even if you are happy to punch out a clean install there is a Windows 8.1 Upgrade Assistant, which will give you an assessment on what is compatible and what isn’t.
Note, if you want the upgrade option, there are several options here, summarised down, these are essentially,
1. Keep Nothing (clean install)
2. Keep Personal Files (make sure your files are in your Desktop or Documents folder)
3. Keep Apps (if you don’t see this try the Professional edition media)
If you get along to here you will find more details about the upgrade process http://windows.microsoft.com/en-au/windows-8/upgrade-from-windows-7-tutorial.