New memory preventing startup

Hi
Ok, I have tried purchasing some new memory for my Windows ME AMD Athlon 950MHz, 100MHz external bus Gateway computer, bought in 2000. It only had 64Mb memory.
I am no expert, but did try hard to make sure I got the right one, using the Gateway web site. Anyway, It appeared I needed PC133 SDRAM DIMM (168pin) Non EEC memory, and I ordered a 512Mb stick.
I installed it this evening and when I boot up, nothing - blank screen. Obviously I believe a memory error.
Now Gateway's site says 133MHz DIMM is what is needed for this machine (based on entering the serial number) however
now reading posts here, I think it should be 100/133MHz. Is there such a thing?
Could anyone help, and give me an idea as to exactly what I should be ordering. I can't return this memory, but I can use it elsewhere, but I would like to know exactly what I should be looking for and ordering.
Hopefully I provided enough information! if not will try and add more.
Thanks

Gatway's website is probably correct. PC133 should work at PC100 speed. Are you sure your motherboard can handle 512 meg of RAM? Some boards can only handle 128 or 256 per slot. If you want 512 you need to buy two x 256. I don't know your board's specs. I tried to look it up but the places I checked all want to know the computer's number. Go to a place like www.18004memory.com or www.crucial.com and see what they recommend for your system. If they don't list the 512 stick than it probably won't work in your system. If they do list it, then suspect you got a back stick of memory.

Thanks for the reply.
I went to the Crucial site and checked out my system and here is the result:
Motherboard Manufacturer MSI (Micro Star)
Motherboard MS-6330 V3.0B (K7T Turbo) CPU Manufacturer AuthenticAMD
CPU Family AMD Athlon processor
CPU Speed 952MHz
Front-side bus speed 100MHz
Currently installed memory 64MB
Maximum Memory Capacity 1536MB
Total number of memory slots 3
Available memory slots 2

Would this give you a better indication? Unfortunately I am not a tech whiz so I don't know exactly what you are looking for.
Thanks

I also found this on the Crucial site:
"Important information about your system
Memory configurations for Windows 95/98/ME with greater than 256MB, require adjusting the Vcache settings as outlined by Microsoft article Q108079."
As I have Windows ME would this apply to me if I can take a stick of 512Mb memory?
Any tips on how to do this if it is the cause of the problem.
Thanks

If you have both the 64 and the 512 stick installed, take out the 64 stick and see if that works. Check out this link: http://www.plasma-online.de/index.h...in9x_512mb.html

It's a work around solution to your problem and talks about the Vcache settings. When you mess around with the boot files: for example sys.ini, make sure you change the name of your file to something like sys.bak (for backup). If you change one of the boot files and your system doesn't like it, you won't be able to boot again. You'll have to boot off a floppy, delete your new sys.ini file and change sys.bak back to sys.ini to get back to where you started.

I tried running without the 64 in, however it wouldn't do anything with the new memory in, in any combination or stand alone.
I am to techno wiz, so I am limited to how far I can go with this. The new memory is larger (i.e.stands higher when in place beside the old 64 stick), however I was sure the specs were ok when I bought it.