S4 strange error when connecting via USB

When I plug my new S4 my PC detects it for like a second and then it goes away, then again it recognizes it for another second and then away again... (I don't know how to express it better, english is not my native language).

I'm studying IT so I made a few basic tests like:

It's not the cable, I checked with others.
It happens in all the USBs.
The S4 works well in two other PCs.
I also have an S3 and that one does work on the problematic PC.
On safe mode it seems to "work" (not sure if Windows fully recognize the phone but at least it does detect it on the Device manager without going away every second).

So I'm thinking is neigher the hardware nor the phone, just the PC, something installed that interferes, am I right?

Where can I start looking, some log, something, or repair something, any help will do...

Thanks!

Guessing youve tried this but Uninstall the drivers in safe mode then replug it in in Normal Windows and also install Samsung KIES as that should help too:

http://downloadcenter.samsung.com/co.../KiesSetup.exe

Good Luck

Alan

I deleted the drivers with other app in normal mode, is that the same? And it's not about Kies, I don't care if I can only see "unknown device", what I want is the device to stay mount, or whatever the name is, and not do the flashing thing...