I bought an SDHC card. I knew about camera compatibility but not desktop memory card slot compatibility or the lack there of. It could be XP. It could be my computer.
My pain is that I hosed my SD card memory reader in my computer. It is toast.
It could be I need to think about moving up to Vista. Or move to Linux. Or get a Mac.
This is my story, the short version is double check if you have an older computer before you put and SDHC card in the memory slot.