When you are applying for an administrative / office position a typical job interview question is "What computer skills do you have and what programs are you comfortable using?"
The most common software currently being used for office work is word processing software like Microsoft Word, spread sheet software like Microsoft Excel, and presentation software like Microsoft Power Point. It's important to refresh your skills with these basic programs.
Depending on the field the office is in, they may have specialized software that works specifically for them. You should research what they are using ahead of time if at all possible. Also, if you have specific experience with a specialized program, be sure to mention it.