I was using Office 2003 and installed Office 2007 during operating system changeover. All my documents are in 2003 file format. Is it possible to switch them to 2007 format? Please help.
There are several ways to tackle this. First, as Hovsep rightly points out, the newer versions of office will open documents in the older format (and will save them) just fine. If you want to convert some of the documents, you could open them in the Office 2007 and save them in the new format, but obviously you would not want to do that with hundreds or thousands of documents.
If you have a lot of documents, and are worried that support for them will drop in the future (as is almost certain to happen at some point), then you can get a batch converter. There are quite a few on available on the internet, but they cost money, and a fair amount of it.
Finally, Microsoft produced an excellent batch conversion tool called the Office File Converter (OFC), which you can download at http://technet.microsoft.com/en-us/library/cc179019%28v=office.14%29.aspx . It will convert all your documents in situ, so I suggest you back up your documents before you starty. It is incredibly quick and the results are very accurate, but unfortunately, the syntax for running it (it's a command line tool) is quite obscure and you may need to spend some time to figure it out. Still, if you have a lot of documents, that's probably the way to go.
you can open office 2003 word document in office 2007 and save to .docx