From Desktop to laptop, seeing the same office.

Hello,
I need a free (hopefully) software that I can put on my laptop so that when my Manager has to see a client in her office (where my desktop computer is), that I can bring my laptop (originally bought for telecommuting) into the outer offices and still be able to connect to my desktop that is in the office she is using.

It got to be too much to use the "stick hard drive" back and forth. I just want to be able to access my desktop from my laptop while in the outer office. (It is NOT a networked computer that I know of).

It's a PC. and I have a Toshiba Laptop if that makes any difference.

(Also, would the anti-virus that is protecting the desktop also protect my laptop since I'd be connecting into it?)

Also, What is the name of a good software (I know I'd probably have to buy it or pay a monthly fee) for telecommuting from home to see my work desktop? I live about 20 miles away from the office and need to be able to work from my desktop in the winter months or anytime I have an emergency at home. (So it's maybe 4 months out of the year).

Thank you!