The new, $40 Anniversary edition of Ad-Aware Pro, Lavasoft's antispyware application, is unfortunately nothing to celebrate. Though it brings in an antivirus engine to supplement its antispyware scans, the program missed a large percentage of malicious files--including adware and spyware--on test scans. And using it is no cakewalk, either.

In scanning tests from AV-Test.org, a German security-product testing organization, Ad-Aware Pro found only 83.6 percent of 111,833 Trojan horses, spyware, and other malware samples. Its performance varied greatly by malware type; for example, though it caught a respectable 96 percent of remote-control "backdoor" malware, it identified only a dismal 77.4 percent of Trojan horses. Most surprisingly, it nabbed only 78.3 percent of adware and spyware.

Despite the addition of antivirus scans, Ad-Aware's performance doesn't hold up when compared with the results from most antivirus programs, which today almost always include antispyware coverage. While the tests for our recent roundup of security suites aren't directly comparable because AV-Test used a different (and much larger) sample set then, the best performers in that group successfully blocked around 99 percent of malware samples.

Ad-Aware came out poorly in our usage tests, too. Immediately after we installed it, the program warned of suspicious files and ran a scan. Ultimately, the files were safe--and actually required for an encryption program. We took the recommended action of allowing access once (rather than quarantining or ignoring the files), which led to a frustrating loop with Ad-Aware displaying the same warning and running the required scan over and over.

Beyond that aggravating experience, we found using Ad-Aware largely straightforward, despite some highly technical references throughout the application to things such as ADS and MRUs. The program's interface contains sections that display program status, allow for easy scheduling or execution of scans, and give you control over some real-time protections such as watching for malicious processes or attempts to access known unsafe Web sites.

The site-blocking feature did successfully block the Zango Web site, which distributes a generally unwanted adware download. But the real-time protection doesn't extend to scanning a file when it's saved to disk, as antivirus programs do. Blocking a Trojan horse or other nasty before it gets onto your PC is a much better tactic than waiting to clean it up later.

Ad-Aware does check files when they're opened, and its behavior is likely meant to allow it to run alongside regular antivirus programs without conflict. Its poor showing at detecting malware means you'd have to run another security program if you wanted effective protection. But considering that antivirus programs can get rid of spyware, cookies, and adware too, Ad-Aware's $40 extra layer doesn't seem worth it.