Follow the steps in Before you install.
The Rational DOORS client for Windows is now Large Address Aware, which increases the amount of available virtual address space. This enables Rational DOORS to address up to 4 GB of memory on 64-bit versions of Windows and up to 3 GB of memory on 32-bit versions. On 64-bit versions of Windows, no modifications to the operating system are required to benefit from the Large Address Aware capability; however, on 32-bit versions of Windows, the user memory allocation must be increased.
To increase the user memory allocation on 32-bit versions of Windows, edit the C:\boot.ini file and add the text /3GB to the end of the startup line that includes the /fastdetect switch. Restart the computer for the change to take effect.
The /3GB switch changes the way the 4 GB virtual address space is divided. Instead of splitting it as 2 GB of user mode virtual address space and 2 GB of kernel mode (operating system) virtual address space, the split is 3 GB of user mode virtual address space and 1 GB of kernel mode virtual address space. Consider these allocations, if you enable this switch on a server.