defragment your hard drive(s) regularly. Weekly is good. Set a regular time slot such that you can do a bit of housekeeping, which will involve running Defragmenter, Disk Cleanup, updating applications, device drivers, backing up etc.
look out for the 'updates available' icon in the notification area, and act on it at your earliest convenience. There is nothing to be gained by holding back on updates, but security of your system could be compromised if you do not update.
keepyour anti-virus program up to date. The year is 2013, so if your program is a 2012 version or older, it is about time to let it go for something newer. Virus detection is not just about virus definitions. The way in which your program detects a virus is as important.
run a spyware detector which has the ability to update and run without intervention from you. Windows Defender is a good choice and is free.
try to maintain free space of around 25% on your hard drive. It will thank you for it by performing better.
attempt to install and run two anti-virus solutions. Thankfully, many anti-virus programs will not load alongside each other.
attempt to install two firewalls. One will cancel the other out anyway.
ever, ever use the facility to compress a hard drive in order to gain some space. In the event of a hard drive crash, file retrieval from a compressed drive is severely compromised.
update device drivers from Windows Update. It can sometimes work ok, and then again, it can and does cause problems for many. Play safe by not doing this.
The ONLY time to ever do this is in the case of an old piece of hardware which no longer gets support direct from its manufacturer.
make any big changes to your computer configuration without first backing up all of your important stuff. Ensure that you also back up your address book and mail folders if you use Microsoft Outlook, Outlook Express, Windows Mail or Windows Live Mail.
install any utility which promises to make your computer faster. This type of utility will ultimately screw your computer big time. Your computer will only ever be as fast as the individual parts, and overall performance will gravitate to the level of the slowest part.