Because it shouldn't cost less to buy a new computer than to fix the one you have.
I can fix most computer problems, including (but not limited to) virus/spyware/other malware infections, general slow performance, start-up troubles, application installation/removal, network/high-speed internet setup, data backup and migration, and hardware troubles. I can also fix many printer problems and can set up other electronics, including televisions, DVDs, etc.
(My rate for website design and software development is the same. An estimate for time involved with these services is usually possible.)
(Cost is the same for house-calls and drop-offs. Some gas/driving time costs may apply for distances greater than 10 miles.)
(Prices are cost of labor only, parts are separate and paid for by the customer)