Final answer:
The slow performance and frequent disk access is likely caused by the system using virtual memory, due to insufficient RAM for the program's demands
Step-by-step explanation:
The most likely reason for the slow performance and disk access is that the system is using virtual memory due to insufficient RAM. When the program uses 1.5 GB of RAM or more, it nearly exhausts the 2 GB of physical memory available. As a result, Windows has to use a portion of the HDD as an extension of the RAM, known as the swap file or paging file. This process is much slower than accessing RAM and leads to the HDD light flashing as it reads and writes to the disk.