Just thought I'd post a solution that I had to a problem
in case anyone else has the same issue.
Thanks Kenji for the solution.
I am running Xerte Onlinetoolkits 2.0 as localhost on my laptop rather than server based.
I was trying to upload archive files that were bigger than 8MB and was informed
by Xerte there was a limit of around 8MB.
We changed the limit by going into C drive > XAAMP > php > php.ini (there are a few php files, it was the configuration settings one)
Open it in wordpad or notepad and search for 'upload'. Change the limit from 2M to whatever you want. (not sure if this stage is redundant or not as the actual limit was around

Then search for 'post_max_size' and the limit should be 8M.
Change this number to whatever size you like.
Hope this helps someone. Thanks.