Internet works for some sites and doesn't work for some sites

I know this is a Off topic for this blog, but it might help or remind you when you run into similar problem.

I was stuck with weird problem, Internet was working for some sites and was not working for some sites, I thought may be it could be internet problem, but it was NOT, my internet was working good.  Since i have habit of running my PC day and night i though PC might need some rest so restart my PC but things were not change even after restart.

Cause of Problem
The point i want to make here is my PC got infected with Virus.  Anytime you stuck in similar situation where your PC is behaving weird or start doing something unusual you should do a virus scan, since it could be virus which has made changes to registry and that is causing all sorts of problem in my case.

Solution
Best solution i personally believe when you feel that your PC is infected with virus is "Restore your system" to last good state, I do believe that antivirus are good and do good job, but i personally don't trust them 100%.

On my Win 7 PC, I did

• Start > All Programs > Accessories > System Tools > "System Restore"

"System Restore" is a utility provided by Microsoft OS which saves a restore point automatically at regular interval of time. (Mostly when you install any programs.)  I know lots of people know about this option but when you are stuck in problem you try to find solution, but in this case i believe solution might not fix the things 100% and it is better to restore your system to last known good state.

System Restore program will allow you an option to select different date of restore point it has made and will restore your PC to that point

• Good thing about System Restore is, it will not delete any of file created by you during this time period, but it will uninstall any of programs installed between that time frame.
• After system restore, I have found everything on my PC is normal.

Other Solutions

• Trust your antivirus, do scan your system and remove virus identified by your antivirus.
• Open MSConfig tool (Run menu > MSConfig) and try to check "Startup" and "Service" tab to see is there any bad program getting started when you start your PC.
• If you consider yourself as registry expert, then you can try to identify what changes are recently made to registry and validate those changes.
• Use third party tools like CCleaner,... to check whether they can help you?

I personally like to restore my system back to good known state, that is the best solution whenever you run into problem.