No, unfortunately personal items stolen out of your vehicle is not covered by your car's liability insurance. Liability insurance is usually property damage and bodily injury and thus pays for damages to another person's property and medical bills when you are at fault in an accident.
If your car was stolen it would be covered under comprehensive coverage. Even under this optional physical damage coverage though your computer would not be covered if stolen from your vehicle. Personal items taken from a car are not usually covered by an auto insurance policy.
You should see if you can make a claim through your homeowners or renter's insurance though for the theft of your computer from your car. These types of insurance policies typically cover damage to your personal effects owned or used by you while anywhere in the world. This includes while you are traveling or while your property is in transit.
Check your homeowners or renters policy to see if the computer would be covered. Keep in mind most policies have a $1000 coverage limit on expensive personal items such as jewelry, furs, cameras, musical instruments and fine art. You can purchase additional coverage for these items if you find this is needed, but this is something to discuss with your insurance agent for your homeowners or renters insurance policy.
If you need to acquire homeowners or renters insurance then you can do so with our partner Safeco through these links or by calling 1-800-936-0356.