Is your system fully updated and well maintained? Running Disk cleanup, Error Checking and Defrag regularly is important. Closing all programs, especially virus scanners...before opening Picture It! / Digital Image Pro is a good idea.
Adding more RAM to your computer might help, and also increasing your paging file as described in the following article may help.
(308417) HOW TO: Set Performance Options
in Windows XP
http://support.microsoft.com/?kbid=308417
I use the following freebie quite frequently to help keep my system clean...I find it to be useful:
CCleaner
http://www.ccleaner.com/
John Inzer