If that is aluminum foil, then get rid of it. Aluminum foil only creates heat when light hits it, not reflect it. Go buy some reflective mylar car shields at walmart or something.
I don't think he is worried about buying too many things for this grow op if he is growing in a desktop.... I think the foil is fine, atleast you are doing something to protect your roots from the light!
But it would be wise to replace the tinfoil if he can be bothered too.
Heat is a very obvious problem in a PC grow, and the tinfoil will most definitely not help.
Otherwise do you plan to add more light? It's probably better to mount the bulbs horizontally, it'll give you a lot more growing space.