Laptop EXTREMELY slow when not connected to network

I use my personal laptop at work (an Inspiron E1505). To do so, I had to put it on the network at work. However, when I am home, my laptop runs extremely slow, sometimes taking several minutes just to open a simple program like the calculator. Web surfing is useless even with Road Runner. Any way to make this faster?

Also, how would I go about removing the computer from the network and would that fix the issue or would I need to wipe the whole thing and start over?