You can change to a larger capacity drive, but it must be an IDE drive. Most newer drives are SATA and not compatible. SSDs are not necessarily the best choice for H3 as they still have a decreased life-span when doing a lot of writing and re-writing....which is something H3 software does quite a lot.
Unless you have a very old drive (more than 4 or 5 years) you probably won't see any benefits from a new drive except for potentially more storage space.
