No it's safe dood. Makes the files that you are using unmovable though so it defrags around those files. Which...can cause fragmentation. So its safe, but not really as efficient.
Like BJD you shouldn't really run anything when defragging your computer. Especially if you download things from the internet, or save/create/edit files. That can disrupt the process. If you do it too much you'll get a message wanting you to restart defrag, or having to quit because of too much activity depending on your OS. If you do it regularly then defragging shouldn't take that long to do. I'll usually leave mine to run while I am out along with other maintenance programs. I was once told as a rule of thumb whenever you install or uninstall programs you should run a defrag.
My defrag has been running since last night and is still in the process of defragging. It's at 69%. Is this length of time unusual? I use windows vista and chrome in case it helps.
^^^It depends on how much honeysuckle is on your computer. Most defrags should last maybe... 3-4 hours, and that's if you've been doing it monthly or bi-weekly. If you've not done it in years, then yeah, it could take a day or two.
It also depends on your processor speed and RAM and everything.
O.O You need to do some serious "spring cleaning". I don't even think my slow as a snail work computer takes more than an hour, and it's going on 7 years old now. Like BJD said though if you haven't done it (or never) then you may was well go out and run some errands or do some shopping, maybe go see a movie, talk a walk in the park, catch up on your sleeping, read a good book (I hear war and peace is good).
Did you run a disc cleanup before you defragged, that usually helps since it will dump unnecessary files.
I started mine at work while typing this and it's at 27% been awhile since I defragged it too. I stopped doing maintenance on them when I got accused of hiding things. My boss can be a real moron sometimes, his son is worse. LOL 37% now.