OK,

CPU 3.06GHz 1.59 GHz, 512MB or RAM
In addition to the above advice, I would suggest that 512Mb is not a large amount of RAM when you are running Windows XP. Personally, I have never built an XP box with less than 1Gb.

1. Use this tool to get rid of the garbage on your box:

http://www.ccleaner.com/

2. Defragment your hard drive.

3. Check your free space on your HDD. You must have at least 20% or 'doze starts to run like a dog.

4. Look at your power saving settings. I don't know that model but the CPU at 3.06/1.59 tells me that it runs at around half speed when on battery power. Make sure that it is not set to this at all times

5. Watch out for background processes such as AV scanning.