Running disk clean up (provides removal of Temporary internet files)
Running disk Defragmentation.
Deleting of cookies from the browsers (Here there is an option of removing your passwords which you don’t want to do it now, but when you are changing your system for some reason don’t forget to remove them. Also if it is a shared system do store any of your password)
Checking the functionality of each system components like Floppy & CD Drive, Sound card, Fans, etc
Removing dust from the internal system. Keep in mind that most components will get loose. There is also a probability of damaging them.
Updating and Recovering the operating system components. (Formatting is considered as the last option because it will have an impact on the life time of the hard disk and every body wants its data, software and settings left intact)
Upgrading your systems components. E.g. increasing RAM, Hard disk size or from CD-ROM to CD-RW, etc
Remember some of the tasks can be done in different ways as per the persons or organizations requirements. E.g. in school environments the annual task may be done on semester base, and software that keeps the original setting every time the system restarts may be used (like freezer).
Short on motherboard, bad power supply or Speaker connected wrongly
Verify all the Expansion slot are placed properly
Chip creep is caused by thermal expansion and contraction which happens during the heating and cooling of components, and causes components such as removable chips to shift position or work their way out of their mounting clips.
When I'm opening a web browser what I'm seeing is an advert/ offensive page, a pop up page and etc. Check the other symptom form www.infopackets.com/news/security/2005/20051115_spyware_infection_symptoms.htm
An ad software is installed in your system
Change the your Home page address back.
Try to remove an known process from the task manager.
Disable unknown programs form msconfig startup files.
Download an anti spyware and malware software and scan your system.