You don't say how old your laptop is, but old computers eventually fail.
Also, over a long time dust accumulates inside the laptop. This dust forms a blanket that traps heat on the chips and the chips begin erratic operations. When the chips work wrong the computer might corrupt a lot of data on the hard drive.
http://en.wikipedia.org/wiki/Computer_cooling#Generators_of_unwanted_heat
Look at the picture on the right of the dust buildup.
Remove the bottom of your laptop and see if there is a dust buildup. You can remove the dust with canned air, do this outside as a big cloud of dust could appear. Don't use a vacuum cleaner because static electricity is created when air moves through the hose and it could cause damage to the chips.
Once cleaned, try the computer again. This won't correct data corrupted on the hard drive. You just want to make sure the keys work, etc.
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You can try another hard drive in the computer. Remove the current hard drive, install a replacement hard drive, and then install the operating system on the hard drive. If the installation goes well, you have a working computer. If it doesn't, you might have to get a new computer.
You don't have to install Windows. You can install Ubuntu or other version of Linux from a CD, the goal is to see if your computer works predictably.
Otherwise, plan on getting another laptop. And get an adapter called a USB-to-harddrive adapter, that way you can use the old drive and access its data from another computer. These usually cost 40 dollars or less.
About that virus, there are several ways to fix your problem.
1. Get a new computer and start over fresh. All your data that has not been corrupted is still on the other computer's harddrive. This is the fastest way.
2. Replace the harddrive in your computer with a new one, install the factory software, and start over. All your data that has not been corrupted is still on the old harddrive. This is the second fastest way.
3. Use software to fully erase the harddrive in your computer, install the factory software, and start over. All your data is gone. This is the third fastest way because fully erasing that harddrive could take several hours.
All of these suggestions are faster than picking away at a failing system. A USB-to-harddrive adapter allows you to access the data on the old drive without getting a virus infection as long as you don't copy any programs and try to install them or run them.
What about paid software like Microsoft Office ? Contact Microsoft about transferring the license from the old computer (or old harddrive) to the new computer (or harddrive).