diff --git a/menu.cpp b/menu.cpp
index 426fb58..2f576c2 100644
--- a/menu.cpp
+++ b/menu.cpp
@@ -84,6 +84,8 @@ enum MENU
 	MENU_HARDFILE_SELECT1,
 	MENU_HARDFILE_SELECT2,
 	MENU_HARDFILE_SELECTED,
+	MENU_HARDFILE_SELECTED2,
+	MENU_HARDFILE_SELECTED3,
 	MENU_LOADCONFIG_1,
 	MENU_LOADCONFIG_2,
 	MENU_SAVECONFIG_1,
@@ -641,7 +643,8 @@ void HandleUI(void)
 		// No UI in unknown cores.
 		return;
 	}
-
+	
+	struct RigidDiskBlock *rdb;
 
 	char *p;
 	char s[40];
@@ -2049,7 +2052,7 @@ void HandleUI(void)
 		OsdWrite(5, s, menusub == 4, 0);
 		OsdWrite(6, "", 0, 0);
 
-		OsdWrite(7,  " Hard disk", menusub == 5, 0);
+		OsdWrite(7,  " Hard disks", menusub == 5, 0);
 		OsdWrite(8,  " Chipset", menusub == 6, 0);
 		OsdWrite(9,  " Memory", menusub == 7, 0);
 		OsdWrite(10, " Audio & Video", menusub == 8, 0);
@@ -2764,6 +2767,56 @@ void HandleUI(void)
 			if (len > sizeof(config.hardfile[num].filename) - 1) len = sizeof(config.hardfile[num].filename) - 1;
 			if(len) memcpy(config.hardfile[num].filename, SelectedPath, len);
 			config.hardfile[num].filename[len] = 0;
+			menustate = checkHDF(config.hardfile[num].filename, &rdb) ? MENU_SETTINGS_HARDFILE1 : MENU_HARDFILE_SELECTED2;
+		}
+		break;
+
+	case MENU_HARDFILE_SELECTED2:
+		m = 0;
+		menumask = 0x1;
+		if (!rdb)
+		{
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, "    Cannot open the file", 0, 0);
+		}
+		else
+		{
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, "      !! DANGEROUS !!", 0, 0);
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, " RDB has illegal CHS values:", 0, 0);
+			sprintf(s,    "   Cylinders: %d", rdb->rdb_Cylinders);
+			OsdWrite(m++, s, 0, 0);
+			sprintf(s,    "   Heads:     %d", rdb->rdb_Heads);
+			OsdWrite(m++, s, 0, 0);
+			sprintf(s,    "   Sectors:   %d", rdb->rdb_Sectors);
+			OsdWrite(m++, s, 0, 0);
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, " Max legal values:", 0, 0);
+			OsdWrite(m++, "   C:65536, H:16, S:255", 0, 0);
+			OsdWrite(m++, "", 0, 0);
+			OsdWrite(m++, "  Some functions won't work", 0, 0);
+			OsdWrite(m++, "  correctly and may corrupt", 0, 0);
+			OsdWrite(m++, "         the data!", 0, 0);
+		}
+		OsdWrite(m++, "", 0, 0);
+		OsdWrite(m++,     "            OK", 1, 0);
+		while (m < OsdGetSize()) OsdWrite(m++, "", 0, 0);
+
+		menusub_last = menusub;
+		menusub = 0;
+		menustate = MENU_HARDFILE_SELECTED3;
+		break;
+
+	case MENU_HARDFILE_SELECTED3:
+		if (select || menu)
+		{
+			menusub = menusub_last;
+			parentstate = menustate;
 			menustate = MENU_SETTINGS_HARDFILE1;
 		}
 		break;
diff --git a/minimig_hdd.cpp b/minimig_hdd.cpp
index d88b179..51e375f 100644
--- a/minimig_hdd.cpp
+++ b/minimig_hdd.cpp
@@ -24,7 +24,6 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "hardware.h"
 #include "file_io.h"
 #include "minimig_hdd.h"
-#include "minimig_hdd_internal.h"
 #include "menu.h"
 #include "minimig_config.h"
 #include "debug.h"
@@ -63,7 +62,7 @@ typedef struct
 {
 	int             enabled;
 	fileTYPE        file;
-	unsigned short  cylinders;
+	unsigned long   cylinders;
 	unsigned short  heads;
 	unsigned short  sectors;
 	unsigned short  sectors_per_block;
@@ -493,32 +492,46 @@ static void GetRDBGeometry(hdfTYPE *pHDF)
 	pHDF->heads = SWAP(rdb->rdb_Heads);
 	pHDF->sectors = SWAP(rdb->rdb_Sectors);
 	pHDF->cylinders = SWAP(rdb->rdb_Cylinders);
-	if (pHDF->sectors > 255)
+	if (pHDF->sectors > 255 || pHDF->heads > 16)
 	{
-		printf("ATTN: Too many sectors per track %d.", pHDF->sectors);
-		if (pHDF->sectors & 1)
+		printf("ATTN: Illegal CHS value(s).");
+		if (!(pHDF->sectors & 1) && (pHDF->sectors < 512) && (pHDF->heads <= 8))
 		{
-			printf(" Odd number of sectors, Cannot translate. Give up! 8-E\n");
+			printf(" Translate: sectors %d->%d, heads %d->%d.\n", pHDF->sectors, pHDF->sectors / 2, pHDF->heads, pHDF->heads * 2);
+			pHDF->sectors /= 2;
+			pHDF->heads *= 2;
 			return;
 		}
 
-		if (pHDF->sectors > 511)
-		{
-			printf(" Really, too many! Give up! 8-E\n");
-			return;
-		}
+		printf(" DANGEROUS: Cannot translate to legal CHS values. Re-calculate the CHS.\n");
 
-		if (pHDF->heads > 8)
-		{
-			printf(" Too many heads (%d). Cannot translate. Give up! 8-E\n", pHDF->heads);
-			return;
-		}
-
-		printf(" Translate: sectors %d->%d, heads %d->%d.\n", pHDF->sectors, pHDF->sectors / 2, pHDF->heads, pHDF->heads * 2);
-
-		pHDF->sectors /= 2;
-		pHDF->heads *= 2;
-	}
+		uint32_t head, cyl, spt;
+		uint32_t sptt[] = { 63, 127, 255, 0 };
+		uint32_t total = pHDF->file.size / 512;
+		for (int i = 0; sptt[i] != 0; i++)
+		{
+			spt = sptt[i];
+			for (head = 4; head <= 16; head++)
+			{
+				cyl = total / (head * spt);
+				if (total <= 1024 * 1024)
+				{
+					if (cyl <= 1023) break;
+				}
+				else
+				{
+					if (cyl  < 16383) 				break;
+					if (cyl  < 32767 && head >= 5) 	break;
+					if (cyl <= 65536)				break;
+				}
+			}
+			if (head <= 16) break;
+		}
+
+		pHDF->cylinders = cyl;
+		pHDF->heads     = (unsigned short)head;
+		pHDF->sectors   = (unsigned short)spt;
+	}
 }
 
 static void write_sector(int unit, uint32_t lba)
@@ -752,12 +765,12 @@ static void SetHardfileGeometry(hdfTYPE *pHDF, int isHDF)
 			{
 				if (cyl < 16383) break;
 				if (cyl < 32767 && head >= 5) break;
-				if (cyl <= 65535) break; // Should there some head constraint here?
+				if (cyl <= 65536) break; // Should there some head constraint here?
 			}
 		}
 		if (head <= 16) break;
 	}
-	pHDF->cylinders = (unsigned short)cyl;
+	pHDF->cylinders = cyl;
 	pHDF->heads = (unsigned short)head;
 	pHDF->sectors = (unsigned short)spt;
 
@@ -806,3 +819,30 @@ unsigned char OpenHardfile(unsigned char unit)
 	FileClose(&hdf[unit].file);
 	return 0;
 }
+
+int checkHDF(const char* name, struct RigidDiskBlock **rdb)
+{
+	fileTYPE file = { 0 };
+
+	*rdb = NULL;
+	if (FileOpenEx(&file, name, O_RDONLY))
+	{
+		*rdb = (struct RigidDiskBlock *)sector_buffer;
+		for (int i = 0; i<16; ++i)
+		{
+			if (!FileReadSec(&file, sector_buffer)) break;
+			if ((*rdb)->rdb_ID == 0x4B534452)
+			{
+				FileClose(&file);
+				(*rdb)->rdb_Heads = SWAP((*rdb)->rdb_Heads);
+				(*rdb)->rdb_Sectors = SWAP((*rdb)->rdb_Sectors);
+				(*rdb)->rdb_Cylinders = SWAP((*rdb)->rdb_Cylinders);
+				return ((*rdb)->rdb_Heads <= 16 && (*rdb)->rdb_Sectors <= 255 && (*rdb)->rdb_Cylinders <= 65536);
+			}
+		}
+
+		FileClose(&file);
+		return 1; // non-HDF file
+	}
+	return 0;
+}
diff --git a/minimig_hdd.h b/minimig_hdd.h
index 57869a3..3df900f 100644
--- a/minimig_hdd.h
+++ b/minimig_hdd.h
@@ -3,8 +3,11 @@
 #ifndef __MINIMIG_HDD_H__
 #define __MINIMIG_HDD_H__
 
+#include "minimig_hdd_internal.h"
+
 // functions
 void HandleHDD(unsigned char c1, unsigned char c2);
 unsigned char OpenHardfile(unsigned char unit);
+int checkHDF(const char* name, struct RigidDiskBlock **rdb);
 
 #endif // __HDD_H__