What are the actual symptoms?
WHS1 or WHS 2011?
Did you restore to a totally blank HDD (the best option)? Did the backup have all partitions backed up including the System Reserved Partition?
Just guessing as there is little information to go on, but I would try booting from your W7 DVD and doing a system repair to restore the boot files.
Phil P.S. If you find my comment helpful or if it answers your question, please mark it as such.