Running new versions of Windows programs (like QuickBooks) in virtual mode on MacBook Pro 15" Core 2 Duo Model A1226 with 2 MB RAM. System response times slowed way down to a crawl. Solution -- more RAM.
Repair -- job of replacing 2x1MB RAM with 2x2MB RAM was simple and straight forward. On start-up new RAM cards were recognized without any problems. System performance improved greatly as expected.
Don't forget to back-up the system before repair. Used Carbon Copy software application.