Framework installation creates a new account called ASPNET.
I'm no expert on all the admin in Windows etc but I once created a stored procedure in SQLServer from code and the default owner was ASPNET. I had to make sure I wrote the owner into it (dbo).
It is the default account for the aspnet worked thread and has a minimual set of permissions to keep everything going.
I don't really know much more than that - here, there is just me and my machine and no other accounts/passwords etc so it's been hard to learn about all that.
All thats happened is that your installation failed to create the ASPNET account, maybe you don't have permissions to create accounts ? maybe it just failed ?
If the latter you could reinstall it and hope it is successful at creating the account next time, or make it yourself.
Name ASPNET
FullName aspnet_wp account
MemberOf User