I have a uses about .5 MB when resident but not doing much. When it actually starts processing it reads somewhere between 50 and 70 files (depending on what it's going to do) and grows to about 4 GB. This period of reading files takes about 25 seconds on Win7 and about 5 minutes on Win10. The Win7 box is a bit more powerful - i7 4771 @ 3.50GHz vs. i7 930 @ 2.80GHz. Both read from SSDs, but the Win7 box SSD is has a SATA-III connection while the Win10 box SSD has a SATA-II connection. Process Explorer shows long periods when the application is not reading anything but shows a nearly constant 12KB/sec "Other" I/O activity. The Win10 system shows nearly constant reads (like around 50 MB/sec, but it varies a lot). I have tried using Resource Monitor but it seems to show I/O activity averaged or accumulated over a 60 second window. I can tell what files have been opened, but not which currently have activity. Somebody on suggested it might be paging activity that is delaying the program, but I have 12GB ram (vs. 16GB on the Win7 box). I don't think that is the problem. Can anybody suggest what I should look at to diagnose this? I really don't want to upgrade my current Win7 system until I understand what is going on.