As this system has an IDE hard drive interface which is obsolete its not recommended investing much time or money in upgrading this systems hardware and software.
It is recommended 2 GB of RAM to be installed.
Refer to the Service Manual when replacing parts.
Try in order latest first, if it doesn’t work try for an older version.
Right click and select properties and run in compatibility mode for Windows Vista.
See Installing the Windows XP version of Dell Quickset in Windows 7 32 Bit.