TFS 2012 doesn't work against Sql2k8

I'm running Sql Server 2008 EEE (180 days) and I cannot install Team Foundation Server trial (90 days):

TF255146: Team Foundation Server requires SQL Server 2008 R2 (10.50.1600) or greater.  The SQL Server instance Enric_1972 you supplied is version 10.0.5500.0.

is there any shortcut? could I upgrade R2 from a evaluation version?

TIA,

Enric

Enric