Hello, I am facing following problems: 1. Whenever I login to my PC, I get MSXML3.dll not compatible with the version of windows you are running. I don't know to what to do, this error comes repeatedly. 2. When I tried to use windows defender to check for new definitions, it comes up with error code:0x800700c1. 3. I cannot even check for new updates. Could you please help me. Thanks, Manju

Hi, Let us focus on the Windows Update issue this time. You may refer to the following links if there is the McAfee program or Microsoft Security Essentials installed: Windows Defender and McAfee Windows Defender and Microsoft Security Essentials If not, this issue can be caused by one of the following factors: 1. Windows Defender service has been stopped or is missing from the Services list. 2. The following registry key or its sub key is missing or corrupt: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend Step 1: Verify the Windows Defender service ---------------------------------------------------- 1. Click "Start", in the "Start Search" bar, type: "services.msc" (without quotes) and press Enter. If you are prompted for an administrator password or confirmation, type the password or provide confirmation. 2. Double click the service "Windows Defender". 3. Click on the "General" tab; make sure the "Startup Type" is "Automatic" or "Manual". Then please click the "Start" button under "Service Status" to start the service. Note: If the Windows Defender service has already started, please temporarily stop the service, restart the computer. If the service is missing or cannot be stopped or restarted, please move on to the following steps to troubleshoot this issue. Step 2: Restore the Windows Defender Registry Key --------------------------------------------------------------- Before we go any further, please refer to the following links to backup the registry key: Back up the registry Then please move on to the steps below to remedy the key. 1. Click "Start", type: "notepad D:\fix.reg" (without the quotes) in the Start Search Bar and press Enter. Choose "Yes" when you are prompted. 2. Copy the following commands between the two ---------- lines (without the lines) and then paste them into the opened Notepad window. ------------------------------------------------- Windows Registry Editor Version 5.00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend] "DisplayName"="@%ProgramFiles%\\Windows Defender\\MsMpRes.dll,-103" "ErrorControl"=dword:00000001 "Group"="COM Infrastructure" "ImagePath"=hex(2):25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,6f,00,\ 74,00,25,00,5c,00,53,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,73,\ 00,76,00,63,00,68,00,6f,00,73,00,74,00,2e,00,65,00,78,00,65,00,20,00,2d,00,\ 6b,00,20,00,73,00,65,00,63,00,73,00,76,00,63,00,73,00,00,00 "Start"=dword:00000002 "Type"=dword:00000020 "Description"="@%ProgramFiles%\\Windows Defender\\MsMpRes.dll,-3068" "DependOnService"=hex(7):52,00,70,00,63,00,53,00,73,00,00,00,00,00 "ObjectName"="LocalSystem" "ServiceSidType"=dword:00000001 "RequiredPrivileges"=hex(7):53,00,65,00,49,00,6d,00,70,00,65,00,72,00,73,00,6f,\ 00,6e,00,61,00,74,00,65,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,\ 65,00,00,00,53,00,65,00,42,00,61,00,63,00,6b,00,75,00,70,00,50,00,72,00,69,\ 00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,52,00,65,00,73,00,\ 74,00,6f,00,72,00,65,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,\ 00,00,00,53,00,65,00,44,00,65,00,62,00,75,00,67,00,50,00,72,00,69,00,76,00,\ 69,00,6c,00,65,00,67,00,65,00,00,00,53,00,65,00,43,00,68,00,61,00,6e,00,67,\ 00,65,00,4e,00,6f,00,74,00,69,00,66,00,79,00,50,00,72,00,69,00,76,00,69,00,\ 6c,00,65,00,67,00,65,00,00,00,53,00,65,00,53,00,65,00,63,00,75,00,72,00,69,\ 00,74,00,79,00,50,00,72,00,69,00,76,00,69,00,6c,00,65,00,67,00,65,00,00,00,\ 00,00 "FailureActions"=hex:80,51,01,00,00,00,00,00,00,00,00,00,03,00,00,00,14,00,00,\ 00,01,00,00,00,60,ea,00,00,01,00,00,00,60,ea,00,00,00,00,00,00,00,00,00,00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend\Parameters] "ServiceDllUnloadOnStop"=dword:00000001 "ServiceDll"=hex(2):25,00,50,00,72,00,6f,00,67,00,72,00,61,00,6d,00,46,00,69,\ 00,6c,00,65,00,73,00,25,00,5c,00,57,00,69,00,6e,00,64,00,6f,00,77,00,73,00,\ 20,00,44,00,65,00,66,00,65,00,6e,00,64,00,65,00,72,00,5c,00,6d,00,70,00,73,\ 00,76,00,63,00,2e,00,64,00,6c,00,6c,00,00,00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend\Security] "Security"=hex:01,00,14,80,04,01,00,00,10,01,00,00,14,00,00,00,30,00,00,00,02,\ 00,1c,00,01,00,00,00,02,80,14,00,ff,01,0f,00,01,01,00,00,00,00,00,01,00,00,\ 00,00,02,00,d4,00,07,00,00,00,00,00,28,00,ff,01,0f,00,01,06,00,00,00,00,00,\ 05,50,00,00,00,b5,89,fb,38,19,84,c2,cb,5c,6c,23,6d,57,00,77,6e,c0,02,64,87,\ 00,0b,28,00,00,00,00,10,01,06,00,00,00,00,00,05,50,00,00,00,b5,89,fb,38,19,\ 84,c2,cb,5c,6c,23,6d,57,00,77,6e,c0,02,64,87,00,00,14,00,fd,01,02,00,01,01,\ 00,00,00,00,00,05,12,00,00,00,00,00,18,00,ff,01,0f,00,01,02,00,00,00,00,00,\ 05,20,00,00,00,20,02,00,00,00,00,14,00,9d,01,02,00,01,01,00,00,00,00,00,05,\ 04,00,00,00,00,00,14,00,8d,01,02,00,01,01,00,00,00,00,00,05,06,00,00,00,00,\ 00,28,00,15,00,00,00,01,06,00,00,00,00,00,05,50,00,00,00,49,59,9d,77,91,56,\ e5,55,dc,f4,e2,0e,a7,8b,eb,ca,7b,42,13,56,01,01,00,00,00,00,00,05,12,00,00,\ 00,01,01,00,00,00,00,00,05,12,00,00,00 [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WinDefend\Enum] "0"="Root\\LEGACY_WINDEFEND\\0000" "Count"=dword:00000001 "NextInstance"=dword:00000001 ----------------------------------------------------- 3. After pasting the above commands, please close the Notepad window. Choose "Yes" when you are prompted to save the file. Choose D:\fix.reg as its name. 4. Click "Start", type: "D:\fix.reg" (without the quotes) in the Start Search Bar and press Enter to run the commands we have pasted. 5. A dialog box will pop-up saying "Are you sure you want to add the information in C:\fix.reg to the registry?". Click "Yes" on this dialog box 6. Reboot the machine. 7. After the machine reboots, please test the issue. Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread. ”