I'm having problems with an emachine running windows xp home edition

my problem is that the pc needed to b upgraded and cleaned so i used a cleaning program call system mechanic and added a ram stick 256 mb. This was friday the pc was working fine so i restarded and went home, so today i went back to my friends house and started it again but it wouldn't start it would ask me if i want to start the pc on safe mode or go into last known good config or start it normal........i went to start normal and it rebooted the pc, tried safe mode did the same thing, and last known good configuration did the same.......................

Can anyone please help