Microsoft Security Essentials has a setting in the rear that helps somewhat for faster scans.. I set mine to limit use to 100% of cpu ... default, if I recall right, was 30%. MSE no matter what the cpu % is set .. seems to always give other programs 1st priority, and sits & waits for the cpu to be unbusy for its little fun fast time slices. Thats probably why it seems to take so long to finish an update or scan. The newer version seems to update fractionally much smaller definition downloads. Which is nice when you push a manual scan!

This is the second Malwarebytes scan after I removed everything I could from the first scan results. Malwarebytes' Anti-Malware 1.35 Database version: 1939 Windows 5.1.2600 Service Pack 3 04/03/2009 11:04:36 PM mbam-log-2009-04-03 (23-04-36).txt Scan type: Full Scan (C:\:) Objects scanned: 119355 Time elapsed: 47 minute(s), 4 second(s) Memory Processes Infected: 0 Memory Modules Infected: 0 Registry Keys Infected: 15 Registry Values Infected: 0 Registry Data Items Infected: 0 Folders Infected: 0 Files Infected: 8 Memory Processes Infected: (No malicious items detected) Memory Modules Infected: (No malicious items detected) Registry Keys Infected: HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\acpi32 (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\acpi32 (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\amd64si (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\amd64si (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\amd64si (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\netsik (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\netsik (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\nicsk32 (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\nicsk32 (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\i386si (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\i386si (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\ati64si (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\ControlSet002\Services\ati64si (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ati64si (Rootkit.Agent) -> Quarantined and deleted successfully. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\fips32cup (Rootkit.Agent) -> Quarantined and deleted successfully. Registry Values Infected: (No malicious items detected) Registry Data Items Infected: (No malicious items detected) Folders Infected: (No malicious items detected) Files Infected: C:\System Volume Information\_restore"415790D9-BB81-41AF-9469-EEC2DB43FA43>\RP997\A0179839.sys (Rootkit.Agent) -> Quarantined and deleted successfully. C:\WINDOWS\system32\drivers\acpi32.sys (Rootkit.Agent) -> Quarantined and deleted successfully. C:\WINDOWS\system32\drivers\amd64si.sys (Rootkit.Agent) -> Quarantined and deleted successfully. C:\WINDOWS\system32\drivers\netsik.sys (Rootkit.Agent) -> Quarantined and deleted successfully. C:\WINDOWS\system32\drivers\nicsk32.sys (Rootkit.Agent) -> Quarantined and deleted successfully. C:\WINDOWS\system32\drivers\fips32cup.sys (Rootkit.Agent) -> Quarantined and deleted successfully. C:\WINDOWS\system32\drivers\i386si.sys (Rootkit.Agent) -> Quarantined and deleted successfully. C:\WINDOWS\system32\drivers\ati64si.sys (Rootkit.Agent) -> Quarantined and deleted successfully.

With the latest version upgrade there was a box to uncheck for the paid trial version. Missing that... at the top of Malwarebytes there is a place to click to return to the free version. I wonder if this is happening in your case? At the top of the box for the free version it should say Malwarebytes Anti-Malware(Free) 2.02.1012

My answer is that every pc should have malwarebytes on it, it catches more than most any other malware scanner out there. It should not be slowing you down however because it is an on demand scanner and is only using resources when you are actually running the manual scan. Do you mean it becomes slow when you are running a scan or it is always slow? You might try doing an uninstall of it then a re-install. but since it only comes on and uses resources when you actually run a scan with it I can not see why it would have any impact at all on the pc. It could be just coincidental that it slowed at that time could be something else contributing, I would look at the task manager and see what seems to be using the most CPU resources.