If you would like to take a drastic measure to fix this problem, just take everything you have on your computer that you want to keep and save it. Burn it onto a CDR, DVD or put it on an external device such as an external hardrive or a memory stick. Make sure you have all the dics that came with your computer. Such as the Operating system CD and the CD which contains your drivers. I believe that disc is called the Dimension Resource CD. Then wipe you hardrive clean. I used a program called D-ban to do this on my computer. It was free and I found it on the internet at http://www.dban.org/
Now that your hardrive is clean and you saved the stuff you wanted to keep, just reload windows by placing the operating system CD into your cd drive and reboot your computer. When the first window opens hit your F12 key then boot from the CD drive. Folow the onscreen directions and this will reload your operating system. Then install all the drivers from the Dell dimension resource CD. WOW!! Now your computer will run like it is brand new. It will seem like you just bought it new. I have done this several times to my computer. It is a little time consuming but it works like a charm. It will also remove a computer virus if you have one.
Other than the solution above I have used the restore points on my computer. If you have set a restore point on your PC from an earlier date you can go back have all the settings changed to that date. Here is a link to information on how to do a system restore. http://www.computeractive.co.uk/computeractive/q-and-a/2230699/pc-help-system-restore
This is easy to do. Good luck with eveything.