The full version requires a serial number. Original CDs had a sticker. On abandonware sites, sometimes a serial.txt file is included. Otherwise, search for "Ulead Photo Express 4.0 serial" (again, gray area).
Ensuring the program has permission to write to system folders. Ulead Photo Express 4.0 Free Download Full Version
Right-clicking the installer and selecting "Troubleshoot compatibility" to run it as a Windows XP program. The full version requires a serial number
Adobe charges monthly. Many open-source alternatives have a learning curve. Ulead Photo Express 4.0 was a one-time purchase—and many users want to reclaim that model. Ulead Photo Express 4.0 Free Download Full Version
Should I help you find that run natively on your current operating system ?