These days hardware is a commodity and a bargain at that. Except for the Apple world which is vertically integrated, just about anybody’s hardware is as good as anyone else’s. There are some manufacturers where what you find in the box is whatever the purchasing manager got cheap that week. Most desktop computers are made of the same bits and pieces. Laptops and space-saver desktops are another story. If the power supply in your tower desktop goes bye-bye, it can be replaced by me for a minimum amount of money an labor. Each laptop is full of custom parts such as the motherboards and powering arrangements. I say powering arrangements since they typically don’t have a separately replaceable power supply. Also since the turnover of models in the industry is so rapid as in “That machine is so last April.”, after a very short while getting parts can be a problem. With laptops I’ll replace a keyboard, add memory or exchange the disk drive, but beyond that I don’t like to meddle with their innards. They all come apart differently and need special procedures to avoid damaging them.
If your computer dies, and it’s not something simple like a disk drive or power supply, and it’s out of warranty, replace it. The new one will be so much faster and more capable that you’ll wonder why you waited. I know that these are tough economic times, and many of my customers are trying to eke out another year with ol’ Betsy, but it might be a better investment to bite the bullet and refresh (that’s an IT word) your desktop and pay me to recover your data and to get you up and running again than it would be to pay me to resuscitate your old machine and then have to refresh in six months.