sql server 2008 r2 installation error

Question

i am trying to install MS sqlserver 2008 r2

its giving this error

<pre lang="text">

SQL Server 2008 R2 - There are validation errors on this page. Click OK to close this dialog box. Review errors at the bottom of the setup page, then provide valid parameters or click Help for more information.</pre>

Note : this error comes on Service account Tab (while installation comes )

I have window 7 

how can i solve it??