ASL.dll is one of the important file which is saved in Windows 7. If you try to jailbreak your iPhone then you might get “asl.dll is missing” errors. To fix the error, try this
Use blackra1n.exe to fix missing asl.dll errors
1. Step Open C:\Program Files (x86)\Common Files\Apple\Apple Application Support (if you are using Windows 64-bit).
2. Step Next, Right click on the ASL.dll and select “open wit”h and browse for blackra1n.exe. Make sure you select the option ‘Always use the selected programs to open this kind of file‘. Make sure you are logged in as an administrator. That should fix any asl.dll erors in Windows 7 or 8.
If the steps provided above do not work for you, then download and copy blackra1n.exe from http://blackra1n.com and paste it to the folder
C:\Program Files (x86)\Common Files\Apple\Apple Application Support and then you will have to run blackra1n.exe from there.