I have an IBM Thinkpad A31 notebook computer (which I bought used). It was working fine. When I bought it, the dimm cover was missing, so I replaced the SODIMM and purchaced and installed a new cover. I also upgraded the OS from Windows 2000 Professional to Windows XP Professional (including service packs 2 and 3). Now it overheats and shuts down constantly, it crashes often, and the most frustrating thing it does is that it won't always boot properly. I turn it on, I hear the hard drive turning, the lights come on, but no display on screen. In addition to these problems, when it does boot up, sometimes it show that I have a 1.9GHz Pentium 4 processor and other times it shows that I have a 1.3GHz processor. If anyone can help me, I would greatly appreciate it. I'm an assistant pastor and at a small church and I really need this computer! The rest of the specs of my machine are:

512 MB ram
60GB hard disk

Thanks for any assistance