Windows 7 File Access Impossible without system crash!

I have an Acer laptop with only 1gb memory and I am a frequent downloader of large files, be it music, video or picture.

I am conservative with my use of memory, and I still possess over half of it free.

However, ever since I downloaded a collection of videos a month or so ago, each time I have attempted to access any file since then has resulted in windows being unresponsive, and leaving me with no alternative but to manually restart my computer, even after patiently waiting up to an hour for it to respond!

This occurs when I attempt to access any default folder (my pictures, my downloads, my computer), or any desktop file (e.g holiday pictures). Singular files, however, say a spreadsheet document on my desktop, open regularly. So I can conclude it is a problem with the file system. As well as this, within my browser I cannot 'save image' neither can I upload an image to a photosharing website or, more importantly, upload my CV to jobsites(!!) as it results in the browser not responding, the whole system freezing, and an inevitable manual restart.

I have relatively good computer knowledge but I am no expert and do not have a clue what is going on. This problem has frustrated me for a while, please help!

Note. I have since deleted the videos which I believe initiated the problem, however there has been no alteration. I have also performed a system restore to an earlier period, again to no avail. I have defragged too

No its not the bsod. More like the system just doesn't respond. Mouse freezes with the circular loading symbol for ages.
Plus when accessing files through browser, the browser doesn't respond.