For a stable and "best" performing installation, your hardware should meet these recommended specifications:
When users look for specific service packs (like an SP2), they are usually seeking:
Service Pack 2 is critical. If you download plain V15.1, you will encounter the infamous "Internal error 10000" when downloading to S7-1500 CPUs. SP2 resolves this. It also improves the speed of the "Consistency Check" by nearly 40%.
Do not search for cracked or torrent versions. They are often bundled with malware, missing critical DLL files, and lack "Extra Quality." A corrupted crack will cause random crashes during compile—the opposite of quality.