Random RAM question

Hi guys, just a quick one...
I'm looking to upgrade the RAM in my system (currently at 512Mb :-/) and was just wondering what I would need to do if I wanted to get a couple of chips with a higher mhz than my current ones.
Would I need to fiddle with the BIOS or anything to get them working correctly or just 'plug in + play'?
I know I can't mix & match speeds but was wondering if it would be too complicated to change completely.
Any help would be greatly appreciated.
Cheers,
Carl
I'm looking to upgrade the RAM in my system (currently at 512Mb :-/) and was just wondering what I would need to do if I wanted to get a couple of chips with a higher mhz than my current ones.
Would I need to fiddle with the BIOS or anything to get them working correctly or just 'plug in + play'?
I know I can't mix & match speeds but was wondering if it would be too complicated to change completely.
Any help would be greatly appreciated.
Cheers,
Carl