diff --git a/Source/Core/Common/Src/MathUtil.h b/Source/Core/Common/Src/MathUtil.h
index ecace1fb4a..a6290ff602 100644
--- a/Source/Core/Common/Src/MathUtil.h
+++ b/Source/Core/Common/Src/MathUtil.h
@@ -161,6 +161,7 @@ void LoadDefaultSSEState();
 float MathFloatVectorSum(const std::vector<float>&);
 
 #define ROUND_UP(x, a)		(((x) + (a) - 1) & ~((a) - 1))
+#define ROUND_DOWN(x, a)	((x) & ~((a) - 1))
 
 
 // Tiny matrix/vector library.
diff --git a/Source/Core/Core/Src/Boot/Boot.cpp b/Source/Core/Core/Src/Boot/Boot.cpp
index 8d000611c8..be82d217dc 100644
--- a/Source/Core/Core/Src/Boot/Boot.cpp
+++ b/Source/Core/Core/Src/Boot/Boot.cpp
@@ -19,6 +19,7 @@
 #include "Common.h" // Common
 #include "StringUtil.h"
 #include "FileUtil.h"
+#include "MathUtil.h"
 
 #include "../HLE/HLE.h" // Core
 #include "../PowerPC/PowerPC.h"
@@ -68,13 +69,13 @@ void CBoot::Load_FST(bool _bIsWii)
 	u32 fstSize    = VolumeHandler::Read32(0x0428) << shift;
 	u32 maxFstSize = VolumeHandler::Read32(0x042c) << shift;
 
-	u32 arenaHigh = 0x817FFFF4 - maxFstSize;
+	u32 arenaHigh = ROUND_DOWN(0x817FFFFF - maxFstSize, 0x20);
 	Memory::Write_U32(arenaHigh, 0x00000034);
 
 	// load FST
 	VolumeHandler::ReadToPtr(Memory::GetPointer(arenaHigh), fstOffset, fstSize);
 	Memory::Write_U32(arenaHigh, 0x00000038);
-	Memory::Write_U32(maxFstSize, 0x0000003c);		
+	Memory::Write_U32(maxFstSize, 0x0000003c);
 }
 
 void CBoot::UpdateDebugger_MapLoaded(const char *_gameID)
diff --git a/Source/Core/DiscIO/Src/VolumeDirectory.cpp b/Source/Core/DiscIO/Src/VolumeDirectory.cpp
index 52e9f4389a..dc76e2e641 100644
--- a/Source/Core/DiscIO/Src/VolumeDirectory.cpp
+++ b/Source/Core/DiscIO/Src/VolumeDirectory.cpp
@@ -16,6 +16,7 @@
 // http://code.google.com/p/dolphin-emu/
 
 #include "Common.h"
+#include "MathUtil.h"
 #include "CommonPaths.h"
 #include "VolumeDirectory.h"
 #include "FileBlob.h"
@@ -23,17 +24,6 @@
 namespace DiscIO
 {
 
-static const u8 ENTRY_SIZE = 0x0c;
-static const u8 FILE_ENTRY = 0;
-static const u8 DIRECTORY_ENTRY = 1;
-static const u64 DISKHEADER_ADDRESS = 0;
-static const u64 DISKHEADERINFO_ADDRESS = 0x440;
-static const u64 APPLOADER_ADDRESS = 0x2440;
-static const u32 MAX_NAME_LENGTH = 0x3df;
-// relocatable
-static u64 FST_ADDRESS = 0x440;
-static u64 DOL_ADDRESS = 0;
-
 CVolumeDirectory::CVolumeDirectory(const std::string& _rDirectory, bool _bIsWii,
 								   const std::string& _rApploader, const std::string& _rDOL)
 	: m_totalNameSize(0)
@@ -44,6 +34,8 @@ CVolumeDirectory::CVolumeDirectory(const std::string& _rDirectory, bool _bIsWii,
 	, m_apploader(NULL)
 	, m_DOLSize(0)
 	, m_DOL(NULL)
+	, FST_ADDRESS(0)
+	, DOL_ADDRESS(0)
 {
 	m_rootDirectory = ExtractDirectoryName(_rDirectory);	
 
@@ -321,7 +313,7 @@ bool CVolumeDirectory::SetApploader(const std::string& _rApploader)
 		copy(data.begin(), data.end(), m_apploader);
 
 		// 32byte aligned (plus 0x20 padding)
-		DOL_ADDRESS = (APPLOADER_ADDRESS + m_apploaderSize + 0x20 + 31) & ~31ULL;
+		DOL_ADDRESS = ROUND_UP(APPLOADER_ADDRESS + m_apploaderSize + 0x20, 0x20ull);
 		return true;
 	}
 	else
@@ -347,7 +339,7 @@ void CVolumeDirectory::SetDOL(const std::string& _rDOL)
 		Write32((u32)(DOL_ADDRESS >> m_addressShift), 0x0420, m_diskHeader);
 
 		// 32byte aligned (plus 0x20 padding)
-		FST_ADDRESS = (DOL_ADDRESS + m_DOLSize + 0x20 + 31) & ~31ULL;
+		FST_ADDRESS = ROUND_UP(DOL_ADDRESS + m_DOLSize + 0x20, 0x20ull);
 	}
 }
 
@@ -367,8 +359,12 @@ void CVolumeDirectory::BuildFST()
 	m_fstSize = m_fstNameOffset + m_totalNameSize;
 	m_FSTData = new u8[(u32)m_fstSize];
 
+	// if FST hasn't been assigned (ie no apploader/dol setup), set to default
+	if (FST_ADDRESS == 0)
+		FST_ADDRESS = APPLOADER_ADDRESS + 0x2000;
+
 	// 4 byte aligned start of data on disk
-	m_dataStartAddress = (FST_ADDRESS + m_fstSize + 3) & ~3;
+	m_dataStartAddress = ROUND_UP(FST_ADDRESS + m_fstSize, 0x8000ull);
 	u64 curDataAddress = m_dataStartAddress;
 
 	u32 fstOffset = 0;		// offset within FST data
@@ -490,7 +486,7 @@ void CVolumeDirectory::WriteEntry(const File::FSTEntry& entry, u32& fstOffset, u
 		m_virtualDisk.insert(make_pair(dataOffset, entry.physicalName));
 
 		// 4 byte aligned
-		dataOffset = (dataOffset + entry.size + 3) & ~3ULL;
+		dataOffset = ROUND_UP(dataOffset + entry.size, 0x8000ull);
 	}
 }
 
diff --git a/Source/Core/DiscIO/Src/VolumeDirectory.h b/Source/Core/DiscIO/Src/VolumeDirectory.h
index 727974a417..0547be3b8a 100644
--- a/Source/Core/DiscIO/Src/VolumeDirectory.h
+++ b/Source/Core/DiscIO/Src/VolumeDirectory.h
@@ -141,6 +141,16 @@ private:
 
 	u64 m_DOLSize;
 	u8* m_DOL;
+
+	static const u8 ENTRY_SIZE = 0x0c;
+	static const u8 FILE_ENTRY = 0;
+	static const u8 DIRECTORY_ENTRY = 1;
+	static const u64 DISKHEADER_ADDRESS = 0;
+	static const u64 DISKHEADERINFO_ADDRESS = 0x440;
+	static const u64 APPLOADER_ADDRESS = 0x2440;
+	static const u32 MAX_NAME_LENGTH = 0x3df;
+	u64 FST_ADDRESS;
+	u64 DOL_ADDRESS;
 };
 
 } // namespace