If you are planning to throw away, gift or upgrade your desktop PC or laptop because its seems slow, better take that decision after evaluating if an upgrade of the following three things :
(1) RAM
(2) HDD to SSD
(3) Move to Desktop Linux
cannot resolve your problem.
The slow down in most computers is either due to RAM requirements going up for the newer OSes and new versions of the application themselves. Or its just that application and OS become so big that an existing HDD simply cannot read or write data from disk that fast. Of course for the latter you need to have a PC/laptop that has SATA controllers built in.
For comparison sake most modern OS work just great with 4G RAM. 2GB is just about enough and 1GB is actually calling for trouble.More RAM means less paging. For applications, an additional 2G-4G of RAM (making the tortal 6-8 GB) will likely ensure that both the app and OS can work very smoothly. Applications can be loaded directly into RAM and run completely from there. And you can do run many of them simultaneously. Similarly an HDD can write at max around 80-100 MB/s sequentially while a SATA III SSD can go 500 MB/s plus and SATA II 200 MB/S plus (that's like a 2-5 times jump).
Most of us do not stress the CPU to 100% (even 50% in most tasks) and its likely that the CPU is underutilized because it can not read fast enough from disk or that the RAM is not enough. Upgrading CPU/motherboard (which means practically get a new computer) is not always the medicine your computer is looking for.
And finally, consider migrating to a stable Desktop Linux Distrubution like Ubuntu 14.04 LTS. It is comparatively much much lighter on computer resources. I have been usingh Ubuntu or a about 2 months and am pretty satisfied with the results.
(1) It's GUI is table and does not crash. My Opensuse/Fedora builds had this problem occasionally
(2) Upgrades do not break things. I used OpenSuse before and frequently encountered this problem.
(3) You can create & edit common MS Office documents (doc/docx, xls/xlsx and ppt/pptx) with supplied Libreoffice
(4) You get access to latest Mozilla Firefox & chrome Browsers
(5) While many commercial and free to use windows software may not be available, many open source equivalents are freely available which can do common tasks like reading/writing PDFs, Zip/unzip files, Rar/unrar files, Image processing using Gimp (instead of Adobe Photoshop) and so on.
(6) Popular Freewares like VLC, XBMC, etc are readily available
(7) Does not suffer from viruses and therefore does not need investment in antivirus software.
The overall idea is that a modern linux desktop ecosystem such as the one above is fully able to all common tasks usually performed with a PC or Mac and do them well. So why spent money on buying expensive new hardware or commercial applications.
Their are ofcourse some limitations
(1) Older laptop or PC motherboards may not support SATA. IDE SSDs are rare and very expensive making an SSD upgrade impossible
(2) A 120 gb ssd may cost you Rs. 4000/-, but for the same price you can buy a 1 TB HDD. So you should use additional external/internal HDD for data and SSD only for OS & applications to be able to retain full function at lower cost. Buying a large capacity SSD will inflate your upgrade cost to unreasonable levels
(3) Their is a lmit to how much RAM your computer can support and whether the RAM is easily available (older DDR., DDR2) in new retail or used market.
Chances are likely that if your computer in 5-6 years old, you will able to carry out the above three changes. Beyond this it becomes a challenging weekend project with compromises made like not able to run many applications simultaneously, running and older linux version, managing with less RAM or no SSD. I have an old 2002 Dell Inspiron 8200 laptop lying around and I understand this pain.
