If Flashtool is too heavy for your Windows 7 32-bit system:
If Flashtool fails for your specific device, consider these: sony xperia flash tool for windows 7 32 bit
Sony’s official tool for unlocked bootloaders. It is designed for developers but works well for restoring stock firmware. If Flashtool is too heavy for your Windows
Additionally, if you are using an older 32-bit laptop (e.g., Intel Atom netbook from 2010), Windows 7 32-bit is often the last officially supported OS. The Sony Xperia Flash Tool for Windows 7 32-bit runs perfectly on as little as 1GB RAM and an old dual-core processor. Intel Atom netbook from 2010)