Yes it is true. You should be able to replace these modules with two 1 GB modules of DDR PC3200 400MHz

 

http://www.techspot.com/vb/topic65114.html

 

hey elg,
i think what your asking is if you can add the 1 gb to the existing 512k of 2100. if HP specs ok the use of 3200 , you can mix the speeds. iif you do,all of the ram will run at the 2100 speed. also if your machine came with 2x256 modules (as Hp did to activate dual channel) adding a single stick of ram will deactivate the dual channel. to keep the memory running in dual channel, you can add your 1GB as 2x512k, or a second 1gb stick.

 

All HP computers specifying PC2100 will take PC3200 or PC2700... but the memory will still run at the speed of the lowest speed module... so no need to mix modules... DDR PC2100 is 266 MHz. PC2700 is 333 MHz, PC3200 is 400 Mhz so there is a difference.

 

All HP info: http://www.techspot.com/vb/topic100655.html