Dear syr, I think, that it would be very good idea to download Microsoft security essentials and install it to Yours computer and try to run atleast quick test. Try to also remember, if You did not turn The computer off by The unusual way, in some cases, registry binary structure can be corrupted or some hydden error resides in The NTFS file system. Unfortunately, The best NTFS file checking is really build in The algorithms used by Windows, checkdisk feature, so try to run Checkdisk of Yours boot harddrive after reboot by using chkdsk /f c: Confirm y and reboot Your system. It is also possible, that NTFS file system is fragmented. For biginning, try to run The following command exactly as i writing it, Letters are case sensitive. rundll32 advapi32.dll ProcessIdleTasks This will simulate The situation, when computer is idle for a longer time and system will perform a special disk defragmentation. Try to also check Yours disk space left and try to check The virtual memory size. The best is to set The virtual memory sizes to The equal values, so The first and second values must be equal. For example, lets assume, that You have 512 MB of free RAM. Try to change The values for virtual memory setting to 1024 MB and 1024 MB, this will prevent to cause pagefile.sys so much fragmented. If nothink of those techniques will help You, i have last two techniques for You. Try to use The following command sfc /scannow This will work for even Windows Vista and Windows7. Last possibility, Try to use projects based on Winbuilder scripting engine to make Yours own Windows live CD and run chkdsk /f c: Or chkdsk /f /r From The created live CD. But I AM afraid, that complex operations for creating live projects by executing Winbuilder scripting engine with complex projects would cause system instability, if somethink is wrong with Yours C language run-time libraryes, because Winbuilder.exe is also written in C language and will very probably use many procedures and functions from Microsoft C run-time libraryes. It is also possible to install pagedefrag, but this program is only awailable for Windows Xp and NT or 2000. But You can safely use boottime defragmentation features of Purandefrag or Defraggler products. Those are The best freeware defragmenters which are supporting boottime defragmentation according my opinion. PiriDefraggler and Puran defrag are really very good. They are able to defragment nomrally locked system files such as page file or registry hives. Try to also analyse, if many applications are not executed during computer startup, those programs can allocate many RAM.