diff --git a/nu/ds.c b/nu/ds.c
new file mode 100644
index 0000000..e81ddff
--- /dev/null
+++ b/nu/ds.c
@@ -0,0 +1,221 @@
+#include <windows.h>
+#include <ntstatus.h>
+
+#include <assert.h>
+#include <ctype.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "hook/iobuf.h"
+#include "hook/iohook.h"
+
+#include "nu/ds.h"
+#include "nu/nvram.h"
+
+#include "util/crc.h"
+#include "util/dprintf.h"
+#include "util/setupapi.h"
+
+#pragma pack(push, 1)
+
+enum {
+    DS_IOCTL_SETUP          = 0x80006004,
+    DS_IOCTL_READ_SECTOR    = 0x80006010,
+};
+
+struct ds_eeprom {
+    uint32_t crc32;
+    uint8_t unk_04[5];
+    char serial_no[17];
+    uint8_t unk_1A[6];
+};
+
+static_assert(sizeof(struct ds_eeprom) == 0x20, "DS EEPROM size");
+
+#pragma pack(pop)
+
+static HRESULT ds_handle_irp(struct irp *irp);
+static HRESULT ds_handle_open(struct irp *irp);
+static HRESULT ds_handle_close(struct irp *irp);
+static HRESULT ds_handle_ioctl(struct irp *irp);
+
+static HRESULT ds_ioctl_get_geometry(struct irp *irp);
+static HRESULT ds_ioctl_setup(struct irp *irp);
+static HRESULT ds_ioctl_read_sector(struct irp *irp);
+
+static const char ds_serial_file[] = "DEVICE/ds.txt";
+static struct ds_eeprom ds_eeprom;
+static HANDLE ds_fd;
+
+HRESULT ds_hook_init(void)
+{
+    HRESULT hr;
+    FILE *f;
+    char c;
+    int i;
+
+    memset(&ds_eeprom, 0, sizeof(ds_eeprom));
+
+    f = fopen(ds_serial_file, "r");
+
+    if (f != NULL) {
+        i = 0;
+
+        for (;;) {
+            if (feof(f) || i >= sizeof(ds_eeprom.serial_no) - 1) {
+                break;
+            }
+
+            c = getc(f);
+
+            if (isspace(c)) {
+                break;
+            }
+
+            ds_eeprom.serial_no[i++] = c;
+        }
+
+        fclose(f);
+    } else {
+        dprintf("Failed to open %s\n", ds_serial_file);
+    }
+
+    ds_eeprom.crc32 = crc32(&ds_eeprom.unk_04, 0x1C, 0);
+
+    hr = iohook_push_handler(ds_handle_irp);
+
+    if (FAILED(hr)) {
+        return hr;
+    }
+
+    hr = setupapi_add_phantom_dev(&ds_guid, L"$ds");
+
+    if (FAILED(hr)) {
+        return hr;
+    }
+
+    ds_fd = iohook_open_dummy_fd();
+
+    return S_OK;
+}
+
+static HRESULT ds_handle_irp(struct irp *irp)
+{
+    assert(irp != NULL);
+
+    if (irp->op != IRP_OP_OPEN && irp->fd != ds_fd) {
+        return iohook_invoke_next(irp);
+    }
+
+    switch (irp->op) {
+    case IRP_OP_OPEN:   return ds_handle_open(irp);
+    case IRP_OP_CLOSE:  return ds_handle_close(irp);
+    case IRP_OP_IOCTL:  return ds_handle_ioctl(irp);
+    default:            return HRESULT_FROM_WIN32(ERROR_INVALID_FUNCTION);
+    }
+}
+
+static HRESULT ds_handle_open(struct irp *irp)
+{
+    if (wcscmp(irp->open_filename, L"$ds") != 0) {
+        return iohook_invoke_next(irp);
+    }
+
+    dprintf("DS: Open device\n");
+    irp->fd = ds_fd;
+
+    return S_OK;
+}
+
+static HRESULT ds_handle_close(struct irp *irp)
+{
+    dprintf("DS: Close device\n");
+
+    return S_OK;
+}
+
+static HRESULT ds_handle_ioctl(struct irp *irp)
+{
+    switch (irp->ioctl) {
+    case IOCTL_DISK_GET_DRIVE_GEOMETRY:
+        return ds_ioctl_get_geometry(irp);
+
+    case DS_IOCTL_SETUP:
+        return ds_ioctl_setup(irp);
+
+    case DS_IOCTL_READ_SECTOR:
+        return ds_ioctl_read_sector(irp);
+
+    default:
+        dprintf("DS: Unknown ioctl %x, write %i read %i\n",
+                irp->ioctl,
+                irp->write.nbytes,
+                irp->read.nbytes);
+
+        return HRESULT_FROM_WIN32(ERROR_INVALID_FUNCTION);
+    }
+}
+
+static HRESULT ds_ioctl_get_geometry(struct irp *irp)
+{
+    DISK_GEOMETRY *out;
+
+    if (irp->read.nbytes < sizeof(*out)) {
+        dprintf("DS: Invalid ioctl response buffer size\n");
+
+        return HRESULT_FROM_WIN32(ERROR_INSUFFICIENT_BUFFER);
+    }
+
+    dprintf("DS: Get geometry\n");
+
+    out = (DISK_GEOMETRY *) irp->read.bytes;
+    out->Cylinders.QuadPart = 1;
+    out->MediaType = 0;
+    out->TracksPerCylinder = 1;
+    out->SectorsPerTrack = 2;
+    out->BytesPerSector = 32;
+
+    irp->read.pos = sizeof(*out);
+
+    return S_OK;
+}
+
+static HRESULT ds_ioctl_setup(struct irp *irp)
+{
+    dprintf("DS: Setup IOCTL\n");
+
+    return S_OK;
+}
+
+static HRESULT ds_ioctl_read_sector(struct irp *irp)
+{
+    struct const_iobuf src;
+    uint32_t sector_no;
+    HRESULT hr;
+
+    hr = iobuf_read_le32(&irp->write, &sector_no);
+
+    if (FAILED(hr)) {
+        return hr;
+    }
+
+    dprintf("DS: Read sector %08x\n", sector_no);
+
+    src.bytes = (const uint8_t *) &ds_eeprom;
+    src.nbytes = sizeof(ds_eeprom);
+    src.pos = 0;
+
+    iobuf_move(&irp->read, &src);
+
+    if (irp->ovl != NULL) {
+        irp->ovl->Internal = STATUS_SUCCESS;
+        irp->ovl->InternalHigh = irp->read.pos;
+
+        if (irp->ovl->hEvent != NULL) {
+            SetEvent(irp->ovl->hEvent);
+        }
+    }
+
+    return S_OK;
+}
diff --git a/nu/ds.h b/nu/ds.h
new file mode 100644
index 0000000..6bca367
--- /dev/null
+++ b/nu/ds.h
@@ -0,0 +1,12 @@
+#pragma once
+
+#include <windows.h>
+
+DEFINE_GUID(
+        ds_guid,
+        0x279A9F67,
+        0x348F,
+        0x41C9,
+        0xA4, 0xC4, 0xDF, 0xDB, 0x8A, 0xE8, 0xE5, 0xE0);
+
+HRESULT ds_hook_init(void);
diff --git a/nu/guid.c b/nu/guid.c
index 3ea1064..75a8ab6 100644
--- a/nu/guid.c
+++ b/nu/guid.c
@@ -1,5 +1,6 @@
 #include <windows.h>
 #include <initguid.h>
 
+#include "nu/ds.h"
 #include "nu/eeprom.h"
 #include "nu/sram.h"
diff --git a/nu/meson.build b/nu/meson.build
index d4aaeaf..301db40 100644
--- a/nu/meson.build
+++ b/nu/meson.build
@@ -8,6 +8,8 @@ nu_lib = static_library(
         capnhook.get_variable('hooklib_dep'),
     ],
     sources : [
+        'ds.c',
+        'ds.h',
         'eeprom.c',
         'eeprom.h',
         'guid.c',