Networking problems

[kcchi]

My sister's computer has been acting weird lately and I'm not sure where the problem is.

 

- It is unable to play certain flash videos (not all of them but most). Youtube is fine

- It cannot perform any types of updates on current software

- It seems unable to finish downloading anything (i.e. it gets to 99% and then fails, also failed when using any kinds of installers to install any program)

- If the download finishes, the file is always corrupted

 

I scanned the computer with Avira, Microsoft Security Essentials and Malwarebytes and didn't find anything. I tried using Chrome, Firefox and IE but got the same results. Tried to update the network card's driver but it didn't work.

 

CPU: AMD A10-5800K APU

MOBO: Gigabyte F2A88XM-D3H

Network card: D-Link DWA-548

 

I'm starting to think there's some problem with the network card itself but seeing as normal internet browsing is fine, I don't see how it can be broken. 

What should I do?

[kcchi]

Boot into a live Linux distro and see if you get the same results.

I'll try that and see how it goes, thanks

[kcchi]

Boot into a live Linux distro and see if you get the same results.

Wow, everything seems to be working flawlessly on Linux. Is the problem Windows then? Should I re-install it or is there another way around?

Thanks for the suggestion btw