Bad computer days

My computer is still not stable. The harddisk light is on all the time while the whole machine seems to slog it so slow that it takes more than 5 minutes to open the IE browser. The whole bootup process takes more than 15 minutes when it takes about 4 minutes usually. Clicking on the 'start' button and the menu takes some minutes to show up! What's going on??? I don't have money to buy or change anything...