Probably the simplest thing for you to do is create a Windows repair disc assuming you have access to another computer. You can get instructions here :-
Note that the disc comes in two flavours - 32 bit and 64 bit - and you need the correct one for your operating system. The tutorial includes instructions on how to use it.
If it doesn't solve your problem you do at least have the option of doing a factory restore. If you do finish up going this route, you need to be aware that this will wipe everything off your hard drive and restore it to the condition it was in when it came out of the factory. This means that you WILL have to re-install all your applications, including your A/V, but more importantly, before you start this process you will need to back up your data - your work, music, photos and so on.
How you back up your data depends on two factors - how much you have, and how much functionality you have on this computer. You can use a USB memory stick for data up to about 64 Gb, I think they go that big. For more than that you will need an external hard drive. If Windows Explorer is working, then use that to copy data to whatever external media you decide to use. If Windows Explorer isn't working, then probably the simplest thing to do is to create a bootable Puppy Linux CD and use that to move your data. you can get information and instructions on how to create and use a Puppy CD here :-
I have used the Puppy method several times and it works very well. Once you have backed up your data, then you are free to go and use the recovery partition to completely re-install Windows. As for your final point - all you need to back up is your own data. Recovery will re-install Windows and you will then have to re-install your applications and finally put your data back where it belongs.
When backing up data there are one or two things that tend to get forgotten, I know - I have forgotten them on occasions. Back up your e-mail contact list and back up your bookmarks and include them both with your data, and if you have any licensed software that you downloaded, save a note of any registration / activation serials needed or else you are likely to be asked to pay for it again !