There are a million reasons why it takes your PC longer to boot up as your system begins to age. No matter the reasons there is always a way to get it to boot up faster if you maintain certain aspects within the machines configuration.
CLEAN UP YOUR START UP PROGRAMS
One of the main reasons why any PC takes a long time to boot up is because of all the programs that are set to boot up with the operating system when you turn your PC on.
To remedy this click on START-->RUN-->Type MSCONFIG. This should bring you to a configuration box with a series of tabs, go to the last tab titled "STARTUP". Uncheck all the programs that you don't want to start up automatically when you boot the computer. This by far is one of the best methods and you will see faster boot times if you clean up this particular area.
Step 2CLEAN YOUR REGISTRY
Every time you install an application it inserts a key into your the registry of your computer, think of it like an index of keys that tells the computer what to do with the application.
As you delete programs that you've installed this registry gets larger and larger and more difficult for your computer to manage, causing it to take longer to load. Lighten the load by cleaning the registry. Below this article are a few links to some of my favorite registry cleaners that work. Most of them on the net are junk.
QUARANTINE YOUR MACHINE WITH AN ANTI-VIRUS
We all know that virues harm your computer but they also slow them down. McCafee, Trend Micro and Symantec make great anti-virus products that help scan your computer for threats that steal vital cpu processes and protect your computer from blowing up. Run these bi-weekly or monthly.
KILL PROCESSES IN YOUR TASK MANAGER
The task manager is the graphical user interface that your PC uses to show your the performance of your machine. To get to it hoover your mouse over the bottom right hand corner of your task bar where the time is displayed.
Then right click and choose the task manager option. From here you can see how much memory each application is using in addition you have the ability to kill the processes if you wish to speed up your computer. If you don't know what the processes does, copy and paste it and search it in Google before you kill it.