Our computer is already protected by Webroot Antivirus, but a window keeps popping up at random times from windows saying if we want to block certain viruses that have been found on our computer and if we want to enable protection, but I am not sure if enabling the protection is safe. Also, windows security alerts wants us to download a virus protection, is it safe and genuine, or is it a virus within itself? (if not, will it affect Webroot Antivirus?)

I am using Windows XP and all of a sudden, when I clicked on the shortcut to MSN Messenger one day (after starting the computer), it didn’t respond. It seems to be "working somehow" (light indicator showing something is happening and the computer is buzzing) but the Messenger window never shows up. I have uninstalled it several times, rebooted, installed again, but to no avail. I have also removed the shortcuts and created new ones. Nothing seems to work. The process is running though – msnmsgr.exe. I don’t know why the computer started behaving this way. I have an antivirus, don’t go to any suspicious sites, etc. Also, quite recently, my Firefox stopped remembering and suggesting form entried used in the past although it is set to do so. Is it possible that my Windows XP need reinstalling or so? I have had the computer for 2 years. I have a RegistryCleaner that I use from time to time (and have used it now again with no improvement) that always finds lots of errors, etc. and fixes them. (Although I suspect it is quite possible that the registry cleaner may have caused some mess too.) If you have any suggestions, I would be grateful. Thanks a lot in advance.
Adding some details:

Thanks, I have done so and all went fine. Except for the fact that it has not solved my problem, unfortunately. I have tried installing it, uninstalling it, cleaning the registry, etc. and all in vain. I have really no idea why it is doing what it is doing. All of a sudden. Any other idea? Thanks a lot in advance.

I had Windows Vista Home Basic (My computer is a Dell) and I was going to reformat because of a bad virus. My bro gave me Vista Home Premium so i used that and started the formatting process. When it finished, i played a game of solitaire and a notice came up saying that hardware acceleration is off (never happened before). When the game opened, the frame rate becomes very low. Im assuming that my graphics card isn’t working properly. I ran DirectX Diagnostics and it didnt detect my graphics card.
I ran Everest and it says that the graphics card is a Standard VGA (if memory serves from 30mins ago).

I bought this computer off ebay a while ago and the seller gave me the following Installation CDs:

o Cyberlink PowerDVD
o Dell Photo All-in-One Printer
o Dell Dimension Computer Software
o Windows Vista Home Basic 32bit
o Dell LCD Flat Panel Monitor
o Norton Anitvirus

I installed them all except the antivirus.

When I opened up my computer (risky for a noob like me :D), I saw three cards (i assumed one was a graphics CARD). I unclipped them and one says Dell Memory and the others have no name. Games were working for me earlier before i uprgraded.

How do i find the graphics card so i can update it?
Is there any other ways to fix this?

Help please ~ ty

My Pc had a virus attack which has hacked registry settings and some of the registry settings got changed due to which I cannot even go to the task manager, Folder Options etc. I have installed the antivirus and cleaned the virus but I cannot reset the registry settings can any one tell me how to reset the default register settings in windows XP.