Purchase a new computer at an electronics retailer that offers on-the-spot financing. These stores will often allow you to fill out an application for a store credit card and receive a near-instant approval. You can then purchase the computer --- and any college-related computer needs such as a printer or scanner --- using the new using credit card.
Take out a small educational loan with your bank. Take a copy of your college schedule or other proof of enrollment as proof for the loan officer. Apply for or negotiate with the bank for an education loan that allows for deferred repayments. Provide the bank with a list of expected purchases so they will give you the exact amount needed for the computer and related equipment.
Use a portion of your student loans for purchasing a computer. Most student loan programs from the government will pay you a stipend or refund periodically. This will allow you purchase a computer and not pay it off until you graduate with the degree.