Inspiron 8000 Memory Upgrade problems

We have Dell Inspiron 8000 running Windows XP and have tried to upgrade the 128 memory it came with (2x64 pC100) to 512 MB (2x256) and the computer will not boot. Memory purchased from great retailer and works fine seperately (i.e. leave one old 64 in and use one new 256) but once we put max memory in (512) the system will not boot up, it starts to but then trips back off. Did BIOS upgrade and didn't help, Dell only wants to sell us their memory and offered no help.

Any ideas on what we should check?

Thanks!

 

That is indeed odd:

http://support.dell.com/support/edocs/systems/plav/sm/specs.htm#1076395

according to that you should be able to use a MAX of 512 megs of ram. Though, they would have to be 2x256 (as you bought). One note: Are these two sticks of ram pc100?

 

Yes, they are both pc100. Is that good or bad?

 

for some reason it wouldnt let me edit, sorry for the double post.

P.S. I think it may be a problem with my hard drive (10 gigs) which i need to upgrade but im short on cash. I also think it could be a problem with the virtual memory? Does the paging file need to be larger than the amount of RAM? We tried to get the paging file to increase but no matter what we did it wouldnt get higher.