Hello raiden,
Not sure what's going on with your lappy, I have the same Dell Inspiron1525 and didn't have an issue after installing SP1.
Could you install it again, then after installation reboot if necessary, then click "Start", then "Run", then copy/paste SFC /scannow in the box and click "OK".
If that doesn't work, you could try locating the .dll, most likely in C:/Windows/System32, copy the .dll and place it on a CD, install SP1, then re-install/re-register the .dll file.
Here's a thread which seems to be the same issue;
Link Removed - Invalid URL
Hope this helps
Don