How to import a certificate (pfx) with a private key in Windows XP - Super User

i tried whole day import certificate in windows xp, failed. did following:

1. create certificate private key (no password):
   

   makecert -sr localmachine -ss -pe -sky exchange -n "cn=testcert" -a sha1 -sv testcert.pvk testcert.cer

2. then put certificate , private key pfx file:
   

   pvk2pfx.exe -pvk testcert.pvk -spc testcert.cer -pfx testcert.pfx

3. import pfx file command-line tool (german system):
   

   winhttpcertcfg.exe -i testcert.pfx -a nt-autoritÄt\netzwerkdinternet explorernst -c local_machine\my error:  unable import contents of pfx file.     please make sure filename , path,     password, correct.

   hint: "nt-autoritÄt\netzwerkdinternet explorernst" --> "nt-authority\networkservice"
   filename ok, , password not set. if set password (e.g. "mypassword") in step 1 , type @ end of step 3:
   

   ... -p mypassword

i got same error. tried import in certificate console (mmc certificate snap-in). there got following error: "der private schlüssel, den sie importieren, erfordert möglicherweise einen dienstanbieter, der nicht installiert ist." --> "the imported private key may require service-supplier not installed". microsoft crypto-service , running.

what else can do?
on windows vista , windows 7, got running without these problems.
need certificate run wcf service.

meanwhile, found reason problem.

some days before trying import certificates private keys, changed directory access rights of location private keys stored. did following:

cacls "c:\dokumente und einstellungen\all users\anwendungsdaten\microsoft\crypto\rsa\machinekeys" /e /g "nt-autoritÄt\netzwerkdienst":r 

after no longer able import certificates containing private keys. revoked particular access right import of certificates worked well.

i not understand, why adding access right result in practically less access rights.

however, hope may of running same problem.