It seems that until version 2007, Microsoft Excel did indeed support XLR format from MS Works and could be used to both open and save spreadsheets in this format just fine. Alas, this is not the case for latest versions of Microsoft Office and same foes for the usual alternatives to Excel, such as OpenOffice.org Calc or LibreOffice.
A viable option would be to get your hands on some old version of Works. It was commonly bundled together with laptops and new computers so you may even have some old Works installation CD at home.Open WKS file Open XLR file
An older office and productivity suite for Windows