Word 2010 will read and edit your Word 2000 .doc files without any problem. It can also save in that format.

If you do have problems, it will be because of option settings. If any problem, write back and someone will take you through it step by step.

It is possible, by the way, to have both programs on your system at the same time. See Graham Mayor's Toolbars and Word 2007/2010 - dual version registry hack