Slow Computer - Malfunctioning Disk Drive

For a while now, our computer has been running slow. I'm not sure why, anti-virus isn't picking up any viruses, but it's just dragging so bad. So bad that it will just freeze until it catches up on commands. No idea why.. I don't think I'm running low on memory, the computer isn't that old.Another problem I've been having for the longest time is the disk drives aren't opening. When I push the open button, it makes a sound like it's going to come out, but it never does. My sister somehow got it to open this morning, and it does open randomly sometimes after pushing the button a couple hundred times, but it is not at all dependable and half the time I can't use it at all. Today we just bought a replacement that I have to install, but before wasting the $62 I want to make sure that there's nothing that can be fixed easily. For a while I was able to use the emergency eject (you know, with the pin hole) but even that won't work anymore. Just need some help, maybe it's something as simple as new drivers but I have replaced them a few times to no avail