If you want to avoid Windows 8 and its manifold problems and your old computer its not working well, you may be able to bring it back by reinstalling Windows, that is if there are no hardware problems. (Update: Windows 8 makes it easy.)
In fact, reinstalling Windows is the only sure way of bringing your computer back to its original state.
There are a lot of other nostrums out there. They may all be safely disregarded. There is no way of knowing what they do not do, and your old computer may have multiple problems of which you're unaware.
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I usually reinstall once a year as my computer slows up.
(Windows was designed as a stand-alone computer system never to be connected to other computers.)
Some computers make it easy to reinstall by keeping a backup copy of the system in a hidden place on your computer. Your manual will guide you. Otherwise you need the original system disks. If you do not find them you may be able to obtain them from the computer maker.
If you are still keeping your documents on your computer and not using the web for storage, you need to get your files off before reinstalling.
You can either drag and drop them to Dropbox or to a thumb drive. Hopefully most of them are there already.
If you are using applications locally in your computer as opposed to cloud apps, you need to have these install disks ready, or switch to cloud-based apps.
Inserting the system disks will start the process. This process will take some time. As it progresses you will need to come back to your computer to move it along from time to time.
Eventually the process will be completed and you can move on to installing any necessary drivers. If you do not have these from the manufacturer, they may be obtained online and transferred to a CD or DVD from another computer.
It is best to gather together your drivers disks and downloads before even starting the reinstall process.
The next step is to install updates. When updating my computer this morning, there were 134 updates or bandages needed to install Windows 7. Windows is an ongoing sieve for security problems!
You also need to install Microsoft Security Essentials to keep new viruses away.
That can be downloaded and put on a disk and installed before connecting to Internet. Otherwise you'll be subject to host of intrusions the moment you connect.
At that point the next step is to install applications, most easily done from internet online.
Hopefully you made a list of these before starting the reinstallation of the operating system.
Then you need to reinstall those files that you backed up from the old system.
The result will then be that you have a brand new system, safe and fast and free of all the problems of your own system, most of which were probably hidden from view.
Of course, you can avoid all of this by simply installing a person of Ubuntu Linux. The Zorin version works like Windows 8 and has none of the security exposures. Besides, it is free. Just download it and burn to disc before installing.
If uncertain of any of this process, there are plenty of resources on internet to guide you through it. Google it.
The big thing is to avoid all those fixes offered as alternatives which do not give you any assurance that your computer is working properly. They may only work for a while or just not work at all.
If you want to wrestle with the woes of Windows 8, and your old computer is blazingly fast, the new install from new disks is especially easy, up to date, and cheap.
Just be aware that it offers very little new and will require plenty of support in the future.
The same applies to a new computer with Windows 8, except that it may cost more for a decently fast device, unless expertly configured, whereas a Mac or tablet will be largely free from the need of future support. Apple is also there to for support.
Your old computer with reinstalled Windows will give you the capability of doing the few things alternatives cannot do well, and save you money.
Dictated from my Nexus 7