Internet problems! Please help!?

On my mums computer, She cannot get on to the internet and when she clicks the Internet Explorer it opens but doesn't load and Mozilla Firefox doesn't even open up a page. My computer works online and we share the same broadband in the same house. She talked to her friend on my computer and he said that's what it could have been is desktop hijacked. And if you can squash in another answer can you help me with my Google problem? I go on Mozilla Firefox and it opens up like normal but lately a sort of offline Google has been popping up. I can type in something and search and it will find the page like usual but I can not go on Google Images. And in the URL or whatever they call it up the top says stuff like "File/KateComputer/:D/" and all of that as if it's a file not a web page. Have someone screwed our computers somehow? Please help and answer back because my mum wants to by a new computer and it might be in the next hour or so and I want her to know that it can be fixed.