The internet itself can be a good source of information for removing these types of viruses. This is the disk that your software and data will be stored on when you're not using it inside your computer. A sales person will advise you here. I like to have as big a hard drive as I can afford because I tend to fill it pretty quickly but it very much depends on the number of software packages that you plan to have and the types of files you store. If you plan to do a lot of work that involves graphics or desk top publishing, then I would recommend a larger than average hard drive.
Most new computers come with a CD drive fitted.
I wouldn't particularly pay more for a faster speed, you won't be using it that often. This is the 'active' memory of the computer that programs and data that you are currently using are stored in. The amount of RAM you have will affect the speed at which the computer works. Go for the most that you can afford, especially if you are planning to use desk top publishing or a graphics program of any type. The greater the speed measure in MHz, the faster your computer will work.