I have user with a MS Excel 2010 spreadsheet with 70,000 rows (that I have even whiddled down to 10,000 rows for testing purposes). When he tries to run a pivot table on one of the fields (grouping the data in that field by ranges), the first grouping works well. The next grouping uses almost 100% of the processing power of the PC (we also noticed it only uses one of the two processors). We built a Xen Desktop and tried in this environment (with LARGE processing power) and it still ate up ALL the processor power. Where should we look for possible issues?