lap top recovery

Hello I have formatted my hard drive I have P-4 2.8 fujitsu siemens, when I installed my windows again, and take properties it is not showing the computer name siemens like before can u please tell me what I should need to do for the logo and reinstallation of winxp bcoz this is not working properly. My windows are crashing when I have run heavy program like games Etc please tell me what I can do ?