Unless you have familiarity working on a command line interface and have a secondary internet connection to search for solutions, i would strongly advise against using linux, it can cause you a lot of grief. You need to already have a decent background with computers to use it.
Here are the most common reasons for a computer slowing down.
1) Spyware/Malware infections
2) Bloatware/unwanted software using system resources
3) Computer is just too old to run your patched (SP2/3) Windows
Here's what i suggest you do:
First thing is find out if the problem is 3rd party software or if its something that's got to do with your OS or hardware. To do this, we need to boot into safe mode.
Reboot your computer. Just after your BIOS screen and just before the windows logo screen, tap on the F8 key a few times (1 click per second)
This will display several boot options. Select Safemode With Networking and hit enter.
You will see a whole bunch of text and the display will look big. This is normal.
Log into your account and try to access the internet. If it runs fast, then your problem is too many programs on your computer or possibly a spyware infection.
If it still runs slow, then maybe your computer is too old/hardware issue or perhaps there is some sort of OS corruption. If the latter is the case, then the only real advice i can give you over the forum is to backup all your important data, wipe your computer clean and reinstall windows.
If the computer runs smooth and internet is fast, then the following may help you resolve it.Reboot your computer and let it boot normally (do not click F8 this time)
You need to scan your system for malicious software. Use Spybot Search and Destroy, its a free antispyware program, one of the most reliable.
http://www.safer-networking.org/en/home/index.html
download>install>update>immunize>scan>clean. Then reboot, scan, clean again. Reboot again.
Once your back in your system. open your add/remove programs window
Start>Control Pannel>Add/Remove programs.
Wait for the list to populate.
Go through the entire list one by one and remove/uninstall any program you do not recognise/use anymore.
do not restart yet.
Open the System Configuration Utility
Start>Run>MSCONFIG
this opens the microsoft system configuration utility.
Click on the startup tab.
uncheck everything on this list except for your antivirus software (expand the command column to see what the location and the name of the executable is to figure out what the program is, for example, c:\program files\McAfee\... is McAfee antivirus software, its legit and safe)
once you have done this step, apply and close.
Restart your computer.
When you are back in, then clear your Firefox/IE/Chrome cache again, make sure you reset them to defaults, change your home page to something simple like google. Then try to browse to the internet and see how your speeds are.
If you are still having issues, then perhaps its time to simply wipe your computer clean and start over from scratch as further troubleshooting can be difficult over a forum.
If after a wipe/reinstall of Windows you are still having issues, then either your computer is simply too old or there's some hardware issues. Either way, best bet might be to fork out a few hundred bucks and get yourself a new budget system.
I hope this helps you resolve your issue.
Cheers
