Do not get sold on buying a new computer just because industry experts say that they are obsolete after 4 years .... Many computer models can be updated and upgraded by simply replacing specific parts and installing new software .... If you cannot decide her you need to buy or repair, here's the basic rule of thumb to guide you in making that decision: Purchase a new computer if the replacement parts or software necessary to bring it up to date cost more than 50% of its original purchase price ....