I just purchased a 500GB Verbatim Acclaim external hard drive I noticed that it came with some software on it, dcreasing its size down to 465GB, I would like to format the drive to have 500GB of space, would this be safe?
You're not actually going to get the whole 500GB - this is because the hard drives companies use decimal bytes for simplicity's sake (it's simpler to write 500GB than 470.3GB (or whatever)); the actual usable amount of space is probably about 470GB at best.
Yes, you can reformat it if you want. Many external drives come with software for "One Touch Backups" and stuff like that so if you format you would lose whatever software came with the external drive.