Many people confuse 'Memory' with 'Hard Drive Storage'. RAM (Random Access Memory) is the internal 'work-space' of the computer. This 'work-space' is where programs run or 'work'. The Disk Drive is the 'File Cabinet'. This is where programs are stored.
If a computer ... feels too slow, it's usually because the PC doesn't have enough memory. - Microsoft®
After the Processor (CPU), Memory (RAM) is the next most important resource a computer has. Having too little RAM becomes a huge 'bottle-neck' that slows the system down considerably.
Click: Start -> right-click My Computer -> click Properties
Adding memory can be the least expensive and yet one of the most significant upgrades you can make to your computer.
Memory cards simply 'plug-in' to slots inside your computer. It is not difficult, and chances are, you know someone who has done it before. You can do it too!
If you have less than 1G, but do not want to install RAM, plugging in a class 6 or class 10 SD card or USB Drive can significantly help speed up Windows Vista & 7 through ReadyBoost.
Just plug the card or USB drive in, and answer: 'Speed up my system' when your prompted.