Performance Gobblers
Spyware.
Some programs, such as 'Real' player, Apple Quicktime viewer or the free version of DivX will send information back down the line, in the background. This slows down your machine and compromises your privacy. Zonealarm firewall keeps out the hackers and gives you some control over programs that try to send your info back down the line.
'Ad-Aware' or Spybot will detect and remove spyware from your programs and dump dubious 'cookies'. Lavasoft (Ad-Aware) say that some programs might not work properly with spyware removed but I have never had that problem. Spybot seems to dig deeper and find more
Dialers
I have heard of a few people who have accidentally installed a small 'dialer' program which silently calls a premium-rate phone number when using a dial-up connection. In one case it ran up a £90 bill. The dialer might show up as a new network connection with a starred out phone number. I saw one calling itself 'default' to look convincing. Just delete it and run Spybot. Prevent dialers and spyware from installing: http://www.javacoolsoftware.com/spywareblaster.html
Background processes.
MS Office insists on installing 'find fast' and 'office startup' in your startup directory. This works in the background to make Office applications start better - but at the cost of nobbling some performance when you do other things. Screensavers can gobble up computer power but usually when it doesn't matter. Turn it off if you burn CDs or use slow processes, such as like video rendering or number crunching.
A too-rigorous antivirus setting can noticably slow down your computer. You might recover some speed if you just let it scan on bootup or schedule it for idle time - but do make sure that it monitors R/W accesses to removable media such as floppy discs. Antivirus software nobbles performance but you must use it - unless you live in a bubble and don't ever use internet, email or removable discs in your PC. Be suspicious of anything that is 'free', such as cracked software. My favourite antivirus, Free AVG' has a nasty habit of doing a complete scan when it is most inconvenient. You can change the schedule but it is easier to pause the scan.
Windows Defender is the free Microsoft spyware scanner and it does the same trick as AVG by scanning when you don't want it to.
Professional audio software companies tell you not to use the ASPI settings, when you first set up the computer. Later models will have enough performance in reserve for it not to be too much of a nobbler.
'DRM' has caused big trouble with Sony materials. It means 'Digital Rights Management' and installs something subtle on the hard drive that even the virus scanners cannot see. Then it gets in the way if you wish to make a backup copy of your CD or whatever (which is supposed to be legal for your own use). In some cases it has caused severe problems and required a complete re-format of the hard disc. This was a particular problem in 2005/6 but should not be a problem with later discs.
Windows Animations, etc.
In Windows XP, there is a setting for maximum performance which turns off lots of minor effects, such as menu animations. I have found that these tweaks make a noticable performance improvement on slower PCs. Press 'Windows' + 'Pause' (together) > Advanced > Settings > Visual Effects.
The system tray (on right of taskbar) might be full of stuff that you don't use, such as dual language keyboard, scheduler, etc. which can be disabled from the control panel if they are not needed.
Lots of Users
Not a very likely problem at home but where I work large numbers of users can slow down the PC if each is allowed to establish their own 'Personal Profile'. In Win 98, this can be disabled in the Control Panel, under Passwords, to force everyone to use the same one. Win 2k/XP has a profile manager to achieve the same effect. Otherwise, each user's own profile will store loads of downloaded files, cookies and different settings for such as the explorer window, etc. After a while some actions, such as opening the windows explorer, will be very slow as each profile is scanned for the individualised settings.
Polish the Registry
Keep the registry clean as it stores all kinds of hardware and software settings which can end up disjointed and full of junk, a bit like disc fragmentation. Download a registry cleaner to keep it in good order. The old 'Regclean' from Microsoft works in all versions of Windows, including 2000 and XP but is unsupported and used at the PC owner's risk. This will often cure problems caused by installing and uninstalling programs.
Two Hard Disc Drives?
A computer expert friend told me that he achieved a 33% increase in PC performance just by moving the swap/paging file to his second HDD. The reason is that whilst there can be simultaneous reads/writes on separate IDE lines you can't do that on just the one. For the same reason, there is a performance increase if the programs are on one drive and the data on another (not another partition on the same drive). This tweak is for the knowledgeable ones to play with - but then they would know this anyway. Also, make sure that DMA is selected in the HDD hardware configuration unless it is a very old PC.
CPU Priority
Multimedia software, such as video editing, might run best with 'processor scheduling' set to 'background services'. Press 'Windows' + 'Pause' (together) > Advanced > Settings > Advanced. This is the same utility that allows you to set the paging file size and location in Win 2k/XP.
