initializing excel 2007

[Gerhard]

I just bought Office 2007 (legitimate) and installed on my pc. I first used
"control panel uninstall" to remove Office 2003. Went thru all the gyrations
and installed office 2007. NOTHING has been the same since. Every time I
clicked on a .doc, .xls, or .ppd the system did not recognize the files and
wanted to reinstall the appropriate software. That is, it asked do you want
to search the internat for a program to open the file or do you want to use a
known program. Fram that point things went straight down. After contacting
the chat help line (and paying $19.99) for one time help, they got me going
somewhat with WORD and POWER POINT to a point that I can use it. When I
click on and .xls file it wants to go through the install routine again. I
let it a few times but it does not remember that I already have excel. I had
NO problems with office 2003.
Other than going back to office 2003, does anybody have any ideas???? Hate
to buy this software and not be able to use it.
While I can reasonably use a computer, I am NOT a wizard at this sort of
thing.
Thank you