DE2_115 SD_Card Audio Player

I have tried compiling the DE2_115_SD_Card_Audio_Player project in Quartus 2. Then clicked on File -> Create/Update -> Create Symbol Files for Current File. It said Symbol file created successfully but I can't find it in the project directory.

After compilation, it shows DE2_115_SOPC:DE2_115_SOPC_inst under the main project in the Project Navigator. Double clicking on it opens the SOPC builder for the project. I tried generating this system again in the SOPC builder but it gives the following errors:

Warning: Entity "altpll" obtained from "altpll.v" instead of from Quartus II megafunction library

Error: Node "c0" is missing source File: C:/Users/.../AppData/Local/Temp/alt5789_2303333993077008292.dir/0027_sopcqmap/altpll.v Line: 243

Error: Node "c1" is missing source File: C:/Users/.../AppData/Local/Temp/alt5789_2303333993077008292.dir/0027_sopcqmap/altpll.v Line: 244

Error: Node "c2" is missing source File: C:/Users/.../AppData/Local/Temp/alt5789_2303333993077008292.dir/0027_sopcqmap/altpll.v Line: 245

Error: Node "c3" is missing source File: C:/Users/.../AppData/Local/Temp/alt5789_2303333993077008292.dir/0027_sopcqmap/altpll.v Line: 246

Error: Node "locked" is missing source File: C:/Users/.../AppData/Local/Temp/alt5789_2303333993077008292.dir/0027_sopcqmap/altpll.v Line: 248

Error: Node "readdata[0]" is missing source File: C:/Users/.../AppData/Local/Temp/alt5789_2303333993077008292.dir/0027_sopcqmap/altpll.v Line: 251

Error: Node "readdata[1]" is missing source File: C:/Users/.../AppData/Local/Temp/alt5789_2303333993077008292.dir/0027_sopcqmap/altpll.v Line: 251

Warning: Quartus II 32-bit Analysis & Synthesis was unsuccessful. 7 errors, 2 warnings

Error: Peak virtual memory: 313 megabytes

Error: Processing ended: Mon Mar 25 14:45:39 2013

Error: Elapsed time: 00:00:01

Error: Total CPU time (on all processors): 00:00:01

I just want to be able to modify the main.c file in NIOS 2 - Eclipse and use it for my own project.