Chrome Redirecting Me To Other Websites

Hi there, I was using chrome for a while, but it's started playing up and redirecting me to wrong websites, like when I've went on the google chrome extensions page from google search it redirects me usually to the google homepage, but sometimes it takes me to this other website, I think something to do with security. Before everything was fine but it then it said google was using a weak algorithm and something to so with a certificate, I'm sorry I'm a little vague because I forgot what it said. I'm not sure if other things are happening on opera, but not long ago I came across a thing i couldn't get out of which was saying I was blocked from the internet because of copyright!

I also uninstalled chrome to see if it worked, but it didn't and I also uninstalled mozilla as well and download them again to see if it worked. but nothing happened.

Also, what free antivirus thing should I get? I can't believe I haven't gotten one sooner, if I had I bet I wouldn't of even gotten into this mess, but I've learnt from it and I'll make sure it'll never happen again.

I really appreciate your help!

EDIT: I guess the security error from chrome only pops up occasionally, here is what it says:
The site's security certificate is signed using a weak signature algorithm!
You attempted to reach chrome.google.com, but the server presented a certificate signed using a weak signature algorithm. This means that the security credentials the server presented could have been forged, and the server may not be the server you expected (you may be communicating with an attacker).
You cannot proceed because the website operator has requested heightened security for this domain.

My friend recommended Avast, will that do the same trick? Or should I used them too? I've already started scanning with avast.

I used avast, but the page I was on went off focus, like the clicker wasn't on the page. I was frustrated with this so i uninstalled it once it finished its scan and I restarted the computer, windows couldn't open so in safe mode it looked for repairs but it couldn't find any so i did a system restore. It said the system restore didn't work but when I restarted it it did. Then I downloaded malwarebytes, avg and microsoft security essentials, then when avg and malwarebytes completed their scanning and when microsoft security essiantals finished downloading I restarted the computer. But the same thing happened again. Now I'm back to my original problem because the system restore sent me back to before all of them. What should I do? And the same security error is popping up when I go on google.

Every time I restart the computer with an antivirus it seems to not be able to open windows 7 again. Please. Help. Me.

can you be more specific? you reboot your PC, but if it has an antivirus program running..it won't fully load the OS?

You only need one antivirus (Microsoft Security Essentials) and one antispyware (Malwarebytes) Uninstall any other security software (AVG, Avast etc).

If running both don't fix your problem, it's probably time to reinstall windows.

Yes eknirb, and reinstall windows? and hiker, they do fix my problems, but when I restart I can't open the os