Today when Excel was opened I saw - Excel cannot complete this task with available resources. I only use MS Excel 2007, because for my accountant job it is most reliable. Does anyone know how to recovery excel 2007?

This is a question/problem for a regular computer forum, not the computer section of the Cakewalk Sonar recording software forum.   If you registered here just for computer help its really not the right place.
 
You haven't listed what OS so I can't point you directly to an applicable forum.  The Windows 7 forum may be a place to start.  www.sevenforums.com
 
If you are using XP or Vista (considering you have Excel 2007) there are other non OS specific forums around.

https://support.microsoft.com/en-us/help/928976/excel-2007-error-excel-cannot-complete-this-task-with-available-resources.
 

fireberd
This is a question/problem for a regular computer forum, not the computer section of the Cakewalk Sonar recording software forum.   If you registered here just for computer help its really not the right place.
 
You haven't listed what OS so I can't point you directly to an applicable forum.  The Windows 7 forum may be a place to start.  
 
If you are using XP or Vista (considering you have Excel 2007) there are other non OS specific forums around.

Thanks for info, but I hope in this category I would find more helpful info.

slartabartfast
https://support.microsoft.com/en-us/help/928976/excel-2007-error-excel-cannot-complete-this-task-with-available-resources.