The zlib1.dll error is a legacy of ePSXe’s long history: old plugin packs and partial downloads circulated for years with missing pieces, and Windows reports the gap the moment the emulator or a plugin tries to load the compression library. On a clean, current install you should not see it at all — which points at the fix.
The clean fix: reinstall from the official package
- Delete the folder your current copy lives in (keep your memcards and sstates folders — copy them aside first).
- Download the current Windows package, ePSXe2018.zip, from the official source via our download page and verify the SHA-256 printed there.
- Extract the entire zip to a fresh folder and run ePSXe.exe from the extracted folder — never from the zip preview. Most zlib1.dll reports come from running a partially extracted copy or bolting a new .exe onto an ancient folder.
- Copy your memcards and sstates back in.
What not to do
Do not download a lone zlib1.dll from a DLL-download site. Those sites are a classic malware vector, the version is a lottery, and dropping random DLLs next to the .exe masks the real problem: a mixed-up install. If an error names a system library, the professional fix is a clean application folder, not a file hunt.
If the error survives a clean install
- Check which component asks for it: if ePSXe opens but the error appears when a specific old external plugin loads, that plugin is the stale piece — switch to the internal core plugins (see how the plugin system works).
- Confirm you are on the 32-bit program’s terms: ePSXe 2.0.18 is a 32-bit executable, which runs fine on 64-bit Windows, but 64-bit plugin DLLs from other sources will not load into it.
- Re-extract with a different archiver if files arrive incomplete; a truncated zip explains several of these legacy errors at once, including the wnaspi32.dll one.