help why didnt norton catch this?

I was having issues w/ norton I thought my pc would suddenly lock up and run cpu at 99 percent and norton console would say it was 99 percent (norton) Id go offline (turn off modem) and shut down norton and it was okay so I assumed it was norton?

 

Someone told me to download a virus scanner can I say the name of it? And it found the following? Is it legit? Why didnt norton find it?

Is norton insight leaving out important files what happen?

 

Registry Keys Infected:

HKEY_CLASSES_ROOT\Interface\{6c51f7e9-8542-4f25-a30f-2060157752e1} (Trojan.Downloader) -> Quarantined and deleted successfully.

HKEY_CLASSES_ROOT\Interface\{9d573d0e-663c-435f-bf31-2c4497373c41} (Trojan.Downloader) -> Quarantined and deleted successfully.

HKEY_CLASSES_ROOT\Interface\{b1e68d42-02c4-465b-8368-5ed9b732e22d} (Trojan.Downloader) -> Quarantined and deleted successfully.

HKEY_CLASSES_ROOT\Interface\{f3777260-7308-464a-baa2-cc492c0ce7d2} (Trojan.Downloader) -> Quarantined and deleted successfully.

HKEY_CLASSES_ROOT\AppID\{90a52f08-64ac-4dc6-9d7d-4516670275d3} (Trojan.Downloader) -> Quarantined and deleted successfully.

 

I again turned off net and norton to scan with this.  No I dont routinely turn off norton.