I installed avast.

Try a clean install of Avast:

Clean Install of Avast:
https://goo.gl/4Ptzkf

I got new error, i restarted in safemode and run the avastclear and got this error: The stub cannot run installer/updater exucutable ‘c:\Users\Tarja\AppData\local\temp_av_iup.t^m-a02400\instup.exe’ (code 0x3).
please tell me some good antivirus i need something. avast wont work or do u have anymore ideas?

this Computer has only 30 gig flash drivé
What do you mean with that ? No SSD, no hdd ?

its normal hardrive but its small and they call it flash drive because its only 30gig
By they i mean one of my friend said that.

Ok, so your friend doesn’t know what (s)he is talking about.
No mather what size a HD is, it is never a flash drive.

You say it is a brand new system.
New HP stream laptops/systems come with Windows 10 installed.
The one you have is upgraded to Windows 10 from a older version.
I’m, wondering if this really is a new system.

Its new for me, i bought it from store that sell’s a lot of electronics called “Anttila” and its very trusted. But i was little worried when i saw the “Windows old folder” and this Computer cost about 300€

Strange, according to HP they put Windows 10 directly on it.
windows.old is created when there is a upgrade from Windows 7 (8, 8.1) to Windows 10.

I must be missing something, but I do not see a reason why avast refuses to install at this moment.
I suggest you submit a ticket and let avast have a look at the problem.
https://support.avast.com

ok thank you, i submitted a ticket. i said to check details from this treath.

Ok, let’s see if they can find the reason.