I had a dream of having my pc back.
That's strange. Why do you dream of this?
I'm trying to think of an idea on what to do on my pc, I miss it
It's understandable to miss an item you've let someone borrow, but you should let the person who borrowed it be finished using it before asking for it back. Otherwise they may not be able to accomplish the task they originally borrowed it for. If they borrowed the pc for work or school they may end up failing an assignment without your pc.
I am going to ask for it back.
It might be for the best. Lending things out is okay, but if you need it back or want it back, it is okay to get back your PC.