Let's see if they moved elsewhere by doing a COMPLETE search of your hard drive for .doc files (we can do it again for .xls files if warranted). To search the entire C: drive in Vista go to Start / Search Box and type in EXT:DOC. As you're typing you'll see two hyperlinks appear just above where you're typing and one will say Search Everywhere. Click on that. That will do a quick indexed search and bring up a dialog box. Click on Advanced Search. Click on the location drop down menu and find Drive C: and click on it. Check the box "include non-indexed, hidden, and system files (may be slow)." Then click on Search. You will now be searching your entire hard drive for the specified file. And yes, it's not a very efficient way of searching the entire drive for a file but that's how it's done in Vista. You can try again for EXT:XLS. Hopefully this will find them. If not, then they are somehow lost or deleted (are all other files OK - pictures, videos, audios, PDF files,...)?
Check the Recycle Bin to see if they are there - if so just restore them and you're back in business.
If you have Vista Business, Vista Ultimate, or Vista Enterprise you may be in luck. They have what is known as Shadow Copies which are saves of deleted or modified files which can be retrieved in case the changes/deletions were done in error. http://www.microsoft.com/windows/windows-vista/features/shadow-copy.aspx with further information on how to use this feature at: http://blogs.techrepublic.com.com/howdoi/?p=145.
If you have Vista Basic or Vista Premium, Shadow Copies is not available; however, there's an alternative that's free and mirrors the functionality of Shadow Copies called Shadow Explorer.http://www.howtogeek.com/howto/windows-vista/recover-files-with-shadow-copies-on-any-version-of-windows-vista/. Though it won't help you this time, it could very well save you in case this happens again.
In case this doesn't work (not all files are available through Shadow Copies - it occurs periodically), here are some additional free recovery programs which might help:
http://www.snapfiles.com/Freeware/system/fwdatarecovery.html(try Recuva ONLY - do not purchase any products that aren’t free – here or in any of the other links – I’m just suggesting the FREE options and have had problems with some of the commercial ones)
http://www.snapfiles.com/get/diskdigger.html(try this second - if it doesn’t work either chances of recovery are very slim but you can try the other options if you wish)
http://www.snapfiles.com/get/easusdfr.html
http://www.snapfiles.com/get/restoration.html
http://www.snapfiles.com/downloads/recuva/dlrecuva.html
http://www.softperfect.com/products/filerecovery/
http://techpaul.wordpress.com/2008/06/23/how-to-recover-your-lost-files/
Files aren't actually deleted until they are overwritten (though they're no longer available through conventional methods). If you decide to try these recovery programs, you should stop using your hard driveimmediately so you don't overwrite the data you are trying to recover. Slave it to another PC and run the recovery from that PC. Even now you may have permanently lost some of them if you're using that same PC. If you can't do that (slave to another PC), you run the risk of overwriting the data with every action you do on the PC (but you still may be able to recover some or most or even all of the files - it's a matter of luck).
Only you can decide if the data is important enough to take the PC to a data recovery expert to recover the files (they will have better programs and equipment to do so than any of us do and than I provided above). Do NOT go to Geek Squad or any of those big store centers - they mostly don't know what they're doing - take it to a data recovery expert. It will cost quite a bit and they usually offer no guarantees. The decision is yours.
Good luck and I hope this helps!
P.S. If it is ONLY Word and Excel files, then I suggest you also post this question in the Office Discussion Group at:http://www.microsoft.com/office/community/en-us/flyoutoverview.mspx where experts in Word and Excel may be able to help (though I doubt it in this case - but it's worth a try).
Lorien - MCSE/MCSA/Network+/A+ --- If this post helps to resolve your issue, please click the "Mark as Answer" or "Helpful" button at the top of this message. By marking a post as Answered, or Helpful you help others find the answer faster.