Address Book Question / Windows 98 to WINXP

My system was locking up on WIN 98, not sure why....I reloaded WIN98 and still same problem so I decided to load WINXP.  No lockups...runs perfectly now.

However, I may have made a big mistake.....not thinking that the Data files for my address book wouldn't still be there. .....ARE THEY?   And if so how do I identify them....and assuming that they are still on the drive....how do I get my NEWER VERSION of OUtlook & OUTLOOK EXPRESS  read it...

Have I made a big mistake???