Computer problem - pages not opening properly?

I have a bit of a problem with my pc....basically, when I got to open an item from my desktop (yahoo etc) the page takes ages to open up and often 2 pages will open up (I only click the desktop logo once) Also it sometimes only opens it to the restore down size so I have to open it full size using the maximise thingy in the top right hand corner. My apologises, I'm a complete novice when it comes to computers so I doing my best to explain it properly! When I have to maximise the page, that often opens another page too and when I try to close it, it takes ages. Its only be like this for a couple of weeks, I've restored the computer back to before this, I've also deleted browsing history and free up some space on my hard disk. Other than that, its working ok. I'd really appreciate any advice. Thanks in advance.