There seems to be a classic example of virus, malware or adware problem here. You gave us no advice of programs used for this and also for 120 gz HDD, 512 mz ram sounds more in line.
Recently upgraded my 1999 Dell with a 120G Hard Drive and added 128 RAM so I now have 256. Bought and installed brand new XP Home with SP2.
System has been running fine, very smooth in fact until this past week. When I restart the computer, the Dell screen comes on then the royal blue screen with white lettering flashes and it shuts down again. It will keep doing this. The only way for me to start up is to F8 and click Enable Boot Logging. Windows comes up and the system runs fine. Logging out is hit or miss. Sometimes very slow, sometimes quickly. Obviously there is a conflict somewhere. Where would I begin? Is there something I should change under the set up?