PExe is a tiny portable tool which can look inside a .EXE file, tell you whether it's .NET or native code, and - if it's .NET - optionally disassemble it, allowing you to look at the core code.

The interface is extremely basic. It can't process multiple files, scan folders or anything else: instead you must click an "Import" button, browse to your target file, then click "Check File" to see if it's a .NET or native program.

If it is .NET, clicking "Disassemble" extracts the program's internals to a folder with the same name as the executable (C:\Programs\File.exe > C:\Programs\File\*.*).

This might be generally useful as a way of looking inside a .NET program, without installing it. You'll see the main executable, documentation, DLLs if there are any, all the main program files.

PExe also creates a file called disassembled.il with the program's code, or at least the low-level version of it. This probably won't tell you much, as you can see from this chunk of Bulk Crap Uninstaller:

 {
 // Method begins at RVA 0x10540
 // Code size 25 (0x19)
 .maxstack 8
 IL_0000: /* 17 |   */ ldc.i4.1
 IL_0001: /* 8D | (01)00007E */ newarr [System/*23000007*/]System.Uri/*0100007E*/
 IL_0006: /* 25 |   */ dup
 IL_0007: /* 16 |   */ ldc.i4.0
 IL_0008: /* 72 | (70)005D7C */ ldstr "https://www.paypal.com/cgi-bin/webscr\?cmd=_s-xclic"
 + "k&hosted_button_id=TB9DA2P8KQX52" /* 70005D7C */
 IL_000d: /* 73 | (0A)000205 */ newobj instance void [System/*23000007*/]System.Uri/*0100007E*/::.ctor(string) /* 0A000205 */
 IL_0012: /* A2 |   */ stelem.ref
 IL_0013: /* 28 | (06)000282 */ call void BulkCrapUninstaller.Forms.MainWindow/*02000020*/::OpenUrls(class [mscorlib/*23000001*/]System.Collections.Generic.IEnumerable`1/*0100000F*/<class [System/*23000007*/]System.Uri/*0100007E*/>) /* 06000282 */
 IL_0018: /* 2A |   */ ret
 } // end of method MainWindow::donateButton_Click

Not what you'd call readable, but at least it allows you to - for example - search code for URLs. And if you do find a reference to Paypal, as there is here, you can see that it looks harmless: it's connected to a Donate button.