As soon as i turn my pc on my internet slows down a lot

[FuzzIVXX]

I built a pc recently and my connection was fine now lately as soon I turn my pc on which is connect directly to my modem it's slows down my internet to 1.5-2.0 mbps even if its just idle. once I shut it down all my wifi devices get 50 mbps which is what is suppose to be at.

Already check for malware viruses and ran cc cleaner but no help
can anyone help me out.

 

[Urumiko]

install a free firewall like comodo.

 

[bleijendeckers]

If your internet gets very slow once your computer is on and returns to fast when your computer is off AND your computer is connected to your modem with a cable and not trough wifi then something on your computer is eating away the bandwidth.

Like Urumiko states, installing a firewall can help. If malware is present on your system then a firewall can take care of that.

Also check for bonafide programs that make excessive use of bandwidth. This means torrent or other downloader programs that might run at full speed and thus use all your bandwidth.
Also, depending on the version of operating system you installed it might require a large number of updates. If you gave it a few days that problem should have fixed itself, if the lack of bandwidth is something very recent this might be it.