Wow. Great article. I'd suggest a 2nd version of this same article once everyone has added comments.
Before I call in the aging PC death squad I take 2 different approaches
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a) is it a home computer or a unique computer in a business or
b) used in a bigger network, and can easily be re-installed or recloned
Top priority goes to RAM and autorun inspection. I do this for a home pc. No need to do this on a business PC that can have XP re-installed fresh. That new tool by microsoft "autoruns" sounds promising, but seems hard to use. I tend to use the start menu, run, msconfig.exe tool. Before working on anyone's compuer, I back up the registry and make a restore point. ( note that Viruses complicate such safety measures. ) I do autorun cleanup for category A computers. Somtimes I clone their entire drive before attempting any repair. I show people all the autorun icons down by their clock in a before and after situation. This tends to be the the best way to extend the life of older computers. Cleaning up autorun makes the PC behave like new, and makes the user very happy, and they learn their lesson not to install too much. Sometimes old home computers have gone through several ISP cycles, who often lie to customers and make them run an ISP CD with all the bloatware. Sometimes the home user is better wiping the drive, and re-installing windows.
As for RAM, that Kingston.com memory tool is good, but I use it only in addition to consulting the vendor by phone or their website, using the model, TAG or ID of the vendor. I've often extended the life of many computers by removing the wrong ram that was ordered in haste and crashes randomly. Ubuntu boot CD roms have a decent memory test that can run overnight and not touch windows on your hard drive.
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While some people swear by defrag, I've never seen it show much life extension. Proper RAM will mean you don't have to worry about disk defragmentation.
I've worked with a lot of computers where the hard drive croaks suddenly even when the SMART utilites are watching it and giving it a good heath report. The best test is to boot from a cd called boot and nuke. It will wipe the drive and do an intensive write and verify test, the final screen is green=good, yellow or red=bad. Below is a good report on drive / SMART death prediction. http://research.google.com/archive/disk_failures.pdf quote: we conclude that models based on SMART parameters alone are unlikely to be useful
Windows 98,ME and 2000 can still run firefox and do word processing, but it's unlikely you can connect a majority of devices or install programs you will need. Same goes for OSX 10.3 All these have one foot in the grave. Another thing I suggest is getting windows XP to version SP2 and then stop there. Turn off updates, disable IE, and install a hardware ethernet firewall. You can find them used or new for $5-$20. I've seen windows computers stay working this way for years, and they don't have any virus protection. I'm guessing XP will have good accessory support till the year 2015. http://pcsupport.about.com/od/browsers/ht/disableiedef.htm If you want to use Windows XP at version SP3 or above, your PC will need to have at least 512MB of ram just to run one program.
If you want to run multipe programs, sound or video I'd suggest well above 512MB. I'd still suggest making Firefox the default browser and disabling IE 7 or 8.
Whenever I revive an aging home or business PC I duplicate the hard drive. If you know a good used parts shop, you should be able to buy 80GIG IDE drives for about $10 each. Use the bootable GPARTED boot cd to clone the old hard drive to the faster 80gig. Leave the old drive inside the case but unpluged. You will get a speed boost and you have a full backup of the OS at an efficient state. It is a ten dollar restore point that can't be taken down by a virus. And it can be used in an office that might have 2 or more machines with the same hardware. Beware of the windows serial and net id fixes after cloning. WGA
And very often before sending the aging PC to a dump, it is best to dump windows and go with Ubuntu 8 ( for 2008) if the user is able to deal with a slightly different desktop and use firefox. Set MS office options to save as DOC, PPT and XLS or get them a google docs account for doing office work.
If you've got an old desktop that can't run Ubuntu 8, it also can't run windows XP, so you might as well dump it in the hands of a e-waste steward listed on ban.org or svtc.org. However, a old slow laptop is worth the extra effort of installing a lighter weight version of xubuntu. It keeps old laptops with small memory on the net with firefox.
Do not install flash verion 10 on older computers. It is a huge processor hog on all platforms, and flash 10 will make your browser so slow you want to buy a new computer. Install flash 9 which works just as well. A computer without flash working is nearly useless on the web. http://kb.adobe.com/selfservice/viewContent.do?externalId=tn_14266