I don't have 2010, but I can't imagine it's too much different than 2007. Most likely you're still using a legacy file type, such as .xls and as a result it says [Compatibility Mode] in your title bar when the file is open.
Save your workbook as one of these three file types depending on your needs.
.xlsb (Excel Binary workbook). If you do not need your file compatible with earlier versions, this will be faster and reduce file size considering the large amount of data you need. Also will allow macros.
.xlsm (Excel Macro-Enabled work book). Has increased comparability with previous versions of excel (they still need a free converter pack from Microsoft)
.xlsx (Excel workbook). Almost the same thing as .xlsm, but will not allow any macros in the file. More secure as potentially malicious code can't be entered.
After the file is saved, close it and reopen it, Compatibility Mode will be gone and you can go up to 1,000,000 rows.