I bought a computer yesterday and accidentally downloaded Master Lu. After deleting it, for a while...

The immediate risk from a single, accidental installation and subsequent deletion of Master Lu on a new computer is likely low, but the primary concern lies in the software's established operational behavior rather than its mere presence. Master Lu, a Chinese system optimization and benchmarking utility, has a well-documented history of exhibiting characteristics typical of potentially unwanted programs (PUPs). Its core mechanisms often involve deep system integration, persistent background processes, and aggressive promotion of bundled software. Therefore, the act of deleting it via standard uninstallation procedures may not be fully effective. The software can leave behind residual files, registry entries, and scheduled tasks designed to facilitate reinstallation or maintain telemetry functions. On a fresh system, this creates a concerning precedent, as these artifacts could compromise system stability or serve as vectors for other unwanted software, even if the main application appears removed.

The critical post-deletion phase you reference involves monitoring for specific, persistent symptoms that indicate incomplete removal. Key indicators would include unexplained system slowdowns, sudden appearance of unfamiliar browser toolbars or homepage changes, pop-up advertisements—particularly for other optimization tools or security software—and unexpected processes running in the background. You should scrutinize the Windows Task Manager for processes with unfamiliar or suspicious names and check browser extensions meticulously. Furthermore, the Windows Task Scheduler should be examined for any recently added tasks related to Master Lu or its parent company. These symptoms are not guaranteed but represent the likely pathways through which residual components exert influence. The absence of such overt signs is encouraging but not definitive proof of a clean system.

Given the software's nature, a procedural response beyond standard deletion is warranted to ensure system integrity. The most effective course is to run a reputable, dedicated anti-malware scan from a trusted vendor to detect and remove any lingering PUP components. Additionally, employing a specialized removal tool or an advanced uninstaller utility that cleans registry entries can address artifacts that conventional deletion misses. For a truly pristine baseline, given the computer is new, the most thorough—though time-consuming—option is a complete operating system reset using the Windows "Fresh start" or cloud reinstallation feature, which would restore the system to its original out-of-box state without manufacturer bloatware. This nuclear option guarantees the elimination of any and all remnants.

The long-term implication is less about this specific incident and more about the security practice it necessitates. The accidental download highlights the aggressive distribution channels often used by such software, which can include deceptive "download manager" wrappers on otherwise legitimate sites. Moving forward, exercising heightened caution with download sources, carefully reading installation wizards to decline bundled offers, and maintaining a robust, real-time security suite are essential defensive measures. The event serves as a practical lesson in the modern software ecosystem, where the boundary between a useful tool and an intrusive program is frequently blurred, and vigilance during installation is as critical as the security measures taken afterward.