There really isn't any problems with Mountain Lion. The main problems that people have is it will not run programs written to run on technology that was put to death seven years ago. If you have any software that was written for PowerPC, or you have hardware that requires a driver to be updated by a company that doesn't support that hardware any more, then you won't want to upgrade.
To determine what programs you have that are PowerPC, open up System Profiler by holding down the option key and select System Profiler from the Apple menu.
Then, select Applications in the Software section. When it finishes loading, sort the columns by Kind and scroll down to find any programs that are labeld PowerPC. All of those will not run on Lion or Mountain Lion. You will have to either update them to versions that will run, or replace them with something else.
Thanks for your response, I have done as you suggest
and have come up with 3 Power PC labels
1) open xml for charts
2) open xml for excel
3) microsoft query
My next question is how will this affect my computer, I dont know if i use these programmes
I only use the computer for general use emails banking etc
Once again thanks for your help
What version of Office do you have? 2008?
All of those are components of Office. Office 2008 and 2011 will run fine on Mountain Lion.
The XML programs are helpers for importing XML data into Excel and the Chart maker. If you need that functionality, I suppose it wouldn't work.
Microsoft Query is only useful if you connect to other data sources (database) to import data into Excel.
I don't imagine it will be a problem.
If you want to check your other applications that you depend on, look here: http://roaringapps.com/apps:table