Word 2007 saved as Word 97 - 2003 problem

When I purchased my new laptop it was factory loaded with Windows Vista and I was told that I would have to buy Office 2007 with Word 2007. I bought a low-end version (there are now many packages of Office)as my budget is very tight. I had problems with my PC and it needed a total hard-drive wipe (as it had been three years since I bought it and had been running it that long).

My PC went into the shop (much to my dread, as it costs so much) and I ended up having to work in Word 2007 in order to keep on top of my work load.

On returnig to the PC it was necessary for me to transfer those letters done in 2007 back to my PC, which was running Word XP. Now I am getting that error message about a runtime error again, which I have not had for ages.

Could the introduction of Word 2007 documents have caused this error? I am wondering if I should back up my normal and create a fresh normal adn transfer my autotext over to the new Normal. Would that clear up this problem?

I know it's difficult to say when you cannot see my computer, but I would appreciate any help I can get.

People are saying that Vista and Word 2007 are nightmares and I don't really agree. I think it's just that it takes to to learn them. Mind you, I do know Microsoft puts things out and then sends out service packs later to correct problems.

TIA