HTC Desire - Problem writing to /system I have an HTC Desire HD Android device. I rooted it with SuperOneClick. I get a # prompt in terminal. adb remount fails. I'm able to remount /system with 

mount -o rw,remount /dev/block/mmcblk0p25 /system


I can now make changes to /system.

The problem is that my changes are erased when I reboot the phone. This is true even if I create a small dummy file, e.g. derf.txt

Also any new apps that I install go in /data/app while the pre-installed apps are in /system/app.

Output of mount is:

mount
rootfs / rootfs ro,relatime 0 0
tmpfs /dev tmpfs rw,relatime,mode=755 0 0
devpts /dev/pts devpts rw,relatime,mode=600 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
/dev/block/mmcblk0p25 /system ext3 rw,relatime,errors=continue,data=ordered 0 0
/dev/block/mmcblk0p26 /data ext3 rw,nosuid,nodev,relatime,errors=continue,data=o
rdered 0 0
/dev/block/mmcblk0p27 /cache ext3 rw,nosuid,nodev,relatime,errors=continue,data=
ordered 0 0
/dev/block/mmcblk0p28 /devlog ext3 rw,nosuid,nodev,relatime,errors=continue,data
=ordered 0 0
none /acct cgroup rw,relatime,cpuacct 0 0
tmpfs /mnt/asec tmpfs rw,relatime,mode=755,gid=1000 0 0
tmpfs /app-cache tmpfs rw,relatime,size=8192k,mode=755,gid=1000 0 0
none /dev/cpuctl cgroup rw,relatime,cpu 0 0
/data/d /data/d debugfs rw,relatime 0 0
/dev/block/vold/179:33 /mnt/sdcard vfat rw,dirsync,nosuid,nodev,noexec,relatime,
uid=1000,gid=1015,fmask=0702,dmask=0702,allow_utime=0020,codepage=cp437,iocharse
t=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 0
/dev/block/vold/179:33 /mnt/secure/asec vfat rw,dirsync,nosuid,nodev,noexec,rela
time,uid=1000,gid=1015,fmask=0702,dmask=0702,allow_utime=0020,codepage=cp437,ioc
harset=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 0
tmpfs /mnt/sdcard/.android_secure tmpfs ro,relatime,size=0k,mode=000 0 0
#


Has anyone seen this? Can you explain why my changes get wiped out when I reboot the phone?

Thank you very much!
Instead of

mount -o rw,remount /dev/block/mmcblk0p25 /system


try 

mount -o rw,remount /system