I want to increase the memory in my box from 512 to 1 Gig .
The book say I have 184 pin ,2.5V DDR Dimm sockets and supports DDR Sdram up to 200/266/333 Mhz memory module .
My question is can I mix 200/266/333 Mhz memory or do I need to find out what stick I have in the box now and match it , if so can I do this without taking it out .

You probably have two sticks in the box (I hope). If it is only one stick, you still do not want to mix.... Mixing memory is bad. Most people buy sticks in pairs - say you want to upgrade and you want 1GB - go buy 2x512MB modules of DDR 333 if your motherboard says it supports it. Just either save or eBay the spare stick (or send it to me, I'll pay frieght ;))

Do not get ECC RAM unless your motherboard/computer manual says to. Regular old unbuffered/unregistered RAM will work fine for your application.

Be careful what brand you're buying. Don't buy Generic. You get what you pay for. Reputable brand names like OCZ (available at NewEgg at a great low price) carries a lifetime warranty and is much faster and longer lasting than the cheapo crap stores like Best Buy and Staples will try to sell you. Also, generic RAM tends to be less compatible and more likely to cause quirks like random reboots (hardware error) which can destroy your other equipment like the hard drive or your software installations like your copy of Windows.

I'll be happy to make some suggestions. If you just want a quick, inexpensive way to get really good RAM shipped to you 2nd day fedex FREE, go to www.crucial.com and use their memory selector - they'll give you the most compatible stuff for your system you'll ever find. Their RAM uses only high-end chips and is guaranteed for life.

Thanks Shifty ; I figured out what stick was in my box and just ordered a duplicate ,of the same brand .KINGSTON .

Sounds good! Kingston is a great brand. Tough part is finding matching part #'s :D