It could be any number of things:

The bios battery could be dead. I would look on ebay and find one and replace it.

The CPU or motherboard or the hard drive or AC adapter or the battery could be dead.

I sugggest you can go to local laptop service center and for a $60+ diagnosis fee they will tell you what is wrong and how much to repair. Should you repair it they will usually apply the diagnosis fee to the repair costs.

I have always wondered why someone would want to upgrade their Operating System to a newer Microsoft OS? Seems like to me similar to suddenly decided to upgrade your car's engine. Most people have no idea what engine is under the hood, much less think of changing it. If it runs fine why change it.

Upgrading is expensive, complicated and rarely improves the users computing experience. Millions of people still use Windows 98 (an 8 year old OS). It is stable and works fine and even though Microsoft will soon stop support it will continue to work fine for many years. It it is not broken why fix it.

All that said the following are the currently known facts related to upgrading. We won't really know until January 2007, if Microsoft actually ships Vista then. The are not known for making deadlines, especially since they will have seven different versions of Vista!

Vista will require a major increase in computing power and hardware. You need at least 512MB RAM (2GB preferred), SVGA 800×600, DirectX 9, a video card with at least 128MB video RAM, a P3-800 (Vista dumbed down) or P3-1 GHz and a big hard drive with a minimum of 60GB for Home Vista to 160GB with all the features turned on. You can find all the gory details at: Microsoft Vista Hardware Specification.

The bottom line is your budget and your intended uses of the laptop. If you only have $500 to spend then you should seriously consider a refurbished laptop. A new one will cost $600 to $700 by the time it shows up at your door.

Most college campuses these days have wireless networks. Older laptops accept wifi cards, which only cost $30. So they are easily upgradeable. Older laptops often do not have working batteries and even on new ones after a year or two the battery may not work. It usually does not matter, as you will mostly used it plugged into a wall outlet. New batteries often don't last more than 2-3 hours. Word processing, e-mail and chat require little in the way of computing resources as they only need about 8MB or RAM and little space on your hard drive. Browsing the web can be done requires only 8MB to open your browser and can be done on a laptop with as little as 64MB of RAM, but I recommend at least 128MB if you do this a lot. If you are a gamer forget about the budget as you might need as much as 2GB RAM, a graphics chip and a very, very fast CPU. Go new and get your parents to open their checkbook very wide. As a minimum you should have an Ethernet card, if you don't get a wifi card, maybe even have both. The ethernet card or connector (if it is built-in) allows you to hook up to the campus network using a cable. So, the long and short of it is type "used laptop" or "refurbished laptop" into google and see which site comes and check out the top 2-3. You might be surprised and find a decent refurbished laptops for an amazing $350.

Maybe. You need to check to see if the graphics chip is upgradeable. You can find that out on the laptop manufacturer's website. In some cases they are soldered on the circuit board in some cases they are in a socket. So, if in a socket it might be possible to replace it. Some of the newer high end laptops have graphics cards, which makes upgrading them much easier.

A second thing that you need to investigate is how much RAM the laptop has? If you are considering replacing the graphics chip for gaming, it might depend upon the games you play. Changing the graphics chip might help but more RAM might be more or just as important. I just upgraded our 3 year old Dell desktop at home for my 12 year old son to 2GB and upgraded the graphics card, now all his games play to his satisfaction. No more complaining.

You can find out the RAM requirements by going the the game manufacturers website and see what they state are the Systems Requirement. You also need to check out the laptops specifations to figure out how much and what type RAM can be added.

The first thing I would check are how the Power Options are set up. These manage the power consumed by your laptop and it is possible they are configured in such a way that the display dims when the laptop is under battery power. You can find these by looking at the power settings in control panel.

A more serious possibility is that the LCD display has an issue. It could be a faulty backlight or a faulty inverter. The backlight is basically the light bulb in the laptop LCD screen. The inverter is a separate piece from the LCD screen. The inverter essentially takes the DC power converts it into AC power and steps-up the voltage to light up the cold cathode fluorescent backlight.

A dim display is often the result of a faulty inverter. This is very expensive to troubleshoot. The best way to determine the cause is by trying either a new LCD screen or a new inverter. Purchase an inverter first as inverters are less expensive than LCD screens. If the laptop is very old and infrequently used it might be less expensive to replace it, rather than repair it.