I have an dell laptop xps M1530 when i press the power button then it show the massage the amount of system memory has changed if you did not change your memory to resolve this issue try to reseat tgh

Two possibilities:
1) A DIMM has gone bad, and the system is indeed reporting correctly. The msg you are getting (in this case) is the best advice. You can turn off the computer, open the cabinet, and push firmly and straight down on each of the modules. [They are in pairs normally, and the only small circuit cards that look like that. The user manual has pictures.]
If this fixes the problem, great. If not, then you should test and/or replace the defective ones. If you have multiple pairs, then you can test them by removing sets one by one, but this may be a bit tricky depending on your configuration. Again, consult the manual.

2) Especially if the box is somewhat old, then the battery backup may be going (or has gone bad). This is also a possibility on some units if the unit has been unplugged for months. The computer configuration memory loses its data, and has to be reset.
You tackle this fairly easily by rebooting and going into the SETUP while the boot is first starting. Should say on the screen (read fast <G>) but usually pressing DEL or one of the functions keys should get you into the setup screen. [It may also be part of the current error msg you are getting.]
This may get you back up and running, but you will still need to have the battery replaced (likely, unless it has been unplugged for quite a long time).

Note that #2 will get you back up (possibly) if you have a bad RAM DIMM as well, but you may not have enough memory left to perform well.