There really is nothing you can take to cure a cold, it's just that simple.
The so-called "cold and flu remedies" available from pharmacists do nothing but alleviate the symptoms and this in itself can prolong the time you spend feeling ill.
How can relieving the symptoms prolong the infection?
Symptoms such as fever and catarrh are the body's natural mechanisms for fighting infection.
Many of the microbes that cause sickness in humans are very sensitive to temperature, and cannot grow at temperatures above the body's normal 37.5°C (98.6°F) . By raising the temperature of the body, as in a fever (pyrexia), the body is attempting to inhibit microbial growth, thereby giving the immune system a chance to react to the invading organism. Paracetamol can be used to bring down mild fevers, to allow you to get a good night's sleep, but generally the fever should be allowed to run it's course. However, excessively high temperatures in adults or fevers in children should always be treated seriously and medical advice sought.
The catarrh produced in the sinuses, nose and throat are in response to infection or irritation of the mucus membranes in those areas. The mucus contains lysozyme which is an enzyme which is active against the cell wall of many (particularly Gram-positive) bacteria. In addition to the antibacterial properties, the mucus also helps wash away any irritants, dead cells, virus particles etc.
There is no evidence that suggests taking zinc, vitamin C, echinacea or anything else will fight the viral infections that cause the common cold. Taking a generic multivitamin may stave off any ill effects of not being able to eat due to the illness, but they will not speed recovery.
Treating the symptoms of a cold, without dealing with the underlying infection has one last effect. By allowing someone who is still infected and shedding virus to feel better, and possibly return to work/school, the cold and flu remedy is aiding the virus in it's spread from person to person.
So what should you do?
By far the best method of returning yourself to health is to stay in bed, drink plenty of fluid and wait it out.