Buy GHOST: it's a great package (formerly Drive Image from PowerQuest):http://www.newegg.com/Product/Product.aspx?Item=N82E16832108456&Tpk=N82E16832108456
Write a drive image of C: to a USB thumb drive.
Replace your 80GB HDD with your new 1TB HDD.
If you don't have a thumb drive, use PartitionWizardhttp://www.partitionwizard.com/
to shrink your C: partition to something manageable
like 30GB; then, format the remainder ~50GB as a data partition.
Then write your drive image of C: to that data partition.
When that's done, install your new 1TB.
Boot from the restore CD that comes with GHOST
and follow the directions.