I have data which was encrypted with WIndows Crypto API, code written in VB6. 
 Now trying to convert the decrypt code to .NET, and i cannot decrypt.  I 
cannot seem to generate the same key.
THis is a code sample from VB
CryptAcquireContext(hcsp, "strAppName", MS_DEF_PROV, PROV_RSA_FULL, 0)
CryptCreateHash(hcsp, CALG_MD5, 0, 0, hhash)
CryptHashDataString(hhash, pwd,Len(pwd), 0)
CryptDeriveKey(hcsp, CALG_RC2, hhash, CRYPT_EXPORTABLE, hkey)
CryptDestroyHash(hhash)
CryptDecrypt(hkey, 0, 1, 0, VarPtr(vbyteData(0)), lngLenDataBuf)
CryptDestroyKey hkey

Here it is in .NET
        'setup CSP
        Dim csp As New 
System.Security.Cryptography.CspParameters(Providertype.PROV_RSA_FULL, 
MS_DEF_PROV, "strAppName")

        'Generate the Key
        Dim zeroSalt() As Byte = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0} 'see 
http://msdn2.microsoft.com/en-US/library/aa387695.aspx
        Dim ivNull() As Byte = {0, 0, 0, 0, 0, 0, 0, 0}
        Dim cdk As New 
System.Security.Cryptography.PasswordDeriveBytes(mstrPwd, zeroSalt, csp)
        cdk.HashName = "MD5"
        Dim key As Byte()
        key = cdk.CryptDeriveKey("RC2", "MD5", 0, ivNull)

        'Decrypt
        Dim rc2CSP As New 
System.Security.Cryptography.RC2CryptoServiceProvider
        Dim transform As System.Security.Cryptography.ICryptoTransform
        transform = rc2CSP.CreateDecryptor(key, ivNull)
        Dim vbytDataOut(vintLen - 1) As Byte
        vbytDataOut = transform.TransformFinalBlock(vbytData, 0, vintLen)

I did an export on the key in VB6 and tried to compare to the .NET key, and 
they do not match.  The only other thing i can think of is the password...  
The password we are using is 128 abnormal characters, so i was thinking maybe 
the way VB6 and .NET handle them going into the API calls is different.  
Also, i was trying to find something about the number of iterations on the 
derivekey, which i can't determine.  The .NET default seems to be 1000, but i 
dont see any mention of iteration in the APIs.