Hope you created a set of backup DVD's, if the hdd is stuffed, then so are you, as it has the recovery partition and Acer will charge you about £40+ for a set of disks.
Now saying that, all is not lost, you could hook up a second hdd and use cloning software to copy the recovery partition.
But before you do that, if the hdd is seen in bios or bios startup screens, it could just be the boot sector has got corrupt, so just boot off a Win7 cd and us ethe repair option to correct this and see if it sorts things out.