Checked my HD this morning and it said 10% defragmented, so thought I'd just set it to defrag to clean it up a bit. I left it doing it about two hours ago and when I came back to it an hour later it was saying "Pass 6: 0% consolidated" and over the last hour is has gone from 0% to 1% and finally now onto 2%. Should it be taking this long? At this rate it'll be going for days. Will anything come to any harm by stopping it now in the middle of the process?

Never mind, it seems to have sorted itself up and has sped up.

A defrag can take pretty long depending on your HD speed, size and fragmentation.

Before defragmenting, clean up your hard drive as much as possible, close down all the possible programs/exes (remove internet cable etc.) or you could just start the computer in a safe mode and still go trough closing them.

It should speed it up considerably.