Software & Apps Windows How to Fix Rapi.dll Not Found or Missing Errors A troubleshooting guide for rapi.dll errors by Tim Fisher General Manager, VP, Lifewire.com Tim Fisher has 30+ years' professional technology support experience. He writes troubleshooting content and is the General Manager of Lifewire. our editorial process Facebook Twitter LinkedIn Tim Fisher Updated on April 14, 2020 Windows The Ultimate Laptop Buying Guide Tweet Share Email Rapi.dll errors are caused by situations that lead to the removal or corruption of the rapi DLL file. The rapi.dll file is used by Microsoft's Windows Mobile Device Center software and the ActiveSync program, both of which are used to sync files between a computer and a mobile device. While a rapi.dll error message is normally seen only on a computer that's missing one of these programs, in some cases, rapi.dll errors could indicate a registry problem, a virus or malware issue, or even a hardware failure. The rapi.dll error message could apply to any program or system that might utilize the file on any of Microsoft's operating systems, including Windows 10, Windows 8, Windows 7, Windows Vista, Windows XP, and Windows 2000. Rapi.dll Errors There are several different ways that rapi.dll errors can show up on your computer. Here are some of the more common ways that you might see rapi.dll errors. Rapi.dll Not FoundThis application failed to start because rapi.dll was not found. Re-installing the application may fix this problemCannot find [PATH]\rapi.dllThe file rapi.dll is missingCannot start [APPLICATION]. A required component is missing: rapi.dll. Please install [APPLICATION] again The context of the rapi.dll error is an important piece of information that will be helpful while solving the problem. Rapi.dll error messages might appear while using or installing certain programs, when Windows starts or shuts down, or maybe even during a Windows installation. How to Fix Rapi.dll Errors Do not download rapi.dll from a "DLL download" website. There are many reasons why downloading a DLL file is a bad idea. If you need a copy of rapi.dll, it's best to obtain it from its original, legitimate source. Start Windows in Safe Mode to complete any of the following steps if you're unable to access Windows normally due to the rapi.dll error. Restore rapi.dll from the Recycle Bin. The easiest possible cause of a "missing" rapi.dll file is that you've mistakenly deleted it. If you suspect that you've accidentally deleted rapi.dll but you've already emptied the Recycle Bin, you may be able to recover rapi.dll with a free file recovery program. Recovering a deleted copy of rapi.dll with a file recovery program is a smart idea only if you're confident you've deleted the file yourself and that it was working properly before you did that. Install Windows Mobile Device Center, the true origin of the rapi.dll file, if you're getting the DLL error in Windows Vista. If you're not sure which link to pick on the download page, see How to Tell If You Have Windows 64-bit or 32-bit. Install Microsoft ActiveSync if you're using Windows XP when you see this DDL error message. This is the program that puts the rapi.dll file on Windows XP computers, so it should be the only install necessary to fix a missing rapi.dll error message. Of the three download options on that page, the only one you need is setup.msi. Try your best to complete this step. Reinstalling the program that provides the rapi.dll file, if possible, is a likely solution to this DLL error. Run a virus/malware scan of your entire system. Some rapi.dll errors could be related to a virus or other malware infection on your computer that has damaged the DLL file. It's even possible that the rapi.dll error you're seeing is related to a hostile program that's masquerading as the file. Use System Restore to undo recent system changes. If you suspect that the rapi.dll error was caused by a change made to an important file or configuration, a System Restore could solve the problem. Run the sfc/scannow System File Checker command to replace a missing or corrupt copy of the rapi.dll file. Since this DLL file is provided by Microsoft, the System File Checker tool might restore it. Install any available Windows updates. Many service packs and other patches replace or update some of the hundreds of Microsoft distributed DLL files on your computer. The rapi.dll file could be included in one of those updates. Reinstall the program that uses the rapi.dll file. If the rapi.dll DLL error occurs when you use a particular program, reinstalling the program should replace the file. Update the drivers for hardware devices that might be related to rapi.dll. If, for example, you're receiving a "The file rapi.dll is missing" error when you play a 3D video game, try updating the drivers for your video card. The rapi.dll file may or may not be related to video cards—this was just an example. The key here is to pay very close attention to the context of the error and troubleshoot accordingly. Roll back a driver to a previously installed version if rapi.dll errors began after updating a particular hardware device's driver. Test your memory and then test your hard drive. I've left the majority of hardware troubleshooting to the last step, but your computer's memory and hard drive are easy to test and are the most likely components that might cause rapi.dll errors as they fail. If the hardware fails any of your tests, replace the memory or replace the hard drive as soon as possible. Repair your installation of Windows. If the individual rapi.dll file troubleshooting advice above is unsuccessful, performing a startup repair or repair installation should restore all Windows DLL files to their working versions Use a free registry cleaner to repair rapi.dll related issues in the registry. A free registry cleaner program may be able to help by removing invalid rapi.dll registry entries that might be causing the DLL error. We rarely recommend the use of registry cleaners. They've been included as an option here as a "last resort" attempt before the destructive step coming up next. Perform a clean installation of Windows. A clean install of Windows will erase everything from the hard drive and install a fresh copy of Windows. If none of the steps above correct the rapi.dll error, this should be your next course of action. All the information on your hard drive will be erased during a clean install. Make sure you've made the best attempt possible to fix the rapi.dll error using a troubleshooting step prior to this one. Troubleshoot for a hardware problem if any rapi.dll errors persist. After a clean install of Windows, your DLL problem can only be hardware related. Need More Help? If you're not interested in fixing this problem yourself, see How Do I Get My Computer Fixed? for a full list of your support options, plus help with everything along the way like figuring out repair costs, getting your files off, choosing a repair service, and a whole lot more.