Deleting anything on the HDD will free up some space.
I think in practical terms you have a choice of three options:
1. Buy a new, larger HDD.
2. Use an external HDD/CDs/DVDs to download photos, documents and other data you want to keep.
3. Go through the content of your HDD and delete everything you really don`t want. Remember that once you empty the Recycle Bin it is gone, you will never see it again.
You could also run a good Registry cleaner (Ccleaner/RegScrupXP or perhaps Advanced System Care - on this month`s PCA disk) which may also free up some room.