[CFIannotti]

I have a SanDisk Ultra 8Gb SD card.Markings on it are:
30 mb/s ,and the SD logo over HC

My problem is, when I insert it into the SD card slot on the front of my computer, the activity light shows, but the card is not detected in "My computer"
My system is:

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft Windows XP Professional, Service Pack 3, 32 bit
Processor: Intel(R) Pentium(R) D CPU 2.80GHz, x86 Family 15 Model 4 Stepping 4
Processor Count: 2
RAM: 2046 Mb
Graphics Card: NVIDIA GeForce 7300 LE, 256 Mb
Hard Drives: C: Total - 226400 MB, Free - 126161 MB; D: Total - 12040 MB, Free - 4694 MB;
Motherboard: ASUSTek Computer INC., EMERY
Antivirus: Microsoft Security Essentials, Updated: Yes, On-Demand Scanner: Enabled

2 other SanDisk Sd cards work, 1GB and 2 GB.
All 3 cards are read by my Canon T3i. I can shoot and record onto all 3. Obviously, the 1 & 2 GB cards can be inserted into the front panel SD card reader, and I can download pictures that way. As the 8 GB card locks up the computer,I merely use the Canon camera to USB port cable to download images when I use the 8GB card.
Is there a mismatch between that style of SD card (30 mb/s)?
I would like help to make it readable,as I want to write MagicLantern camera software to it. I have the software on the 2 GB card, so i know that is not an issue.
Thanks in advance.

[Gr3iz]

It would appear that your reader is old enough that it doesn't read the HC (high capacity) cards. I ran into the same thing a few years back when I got my first 4GB SDHC. You can get a USB reader fairly cheaply. Mine will allow me to insert full-size, mini and micro SD cards, all at the same time, if I wish, and it looks like a fat flash drive.

[CFIannotti]

Thank you Mark.
That was one possibility I assumed I may run into.
2 things I will look into, will be the largest available "ordinary" card, or,as you use, a card reader. Off to Newegg and others.

[Gr3iz]

I believe the largest non HC card is 2GB. With the size of digital photos these days, you really want something larger. The HC cards are probably faster, too. Note the "Class" number.

[CFIannotti]

Thanks. Agreed, As I will be experimenting with video from the camera, I will purchase larger capacity cards down the road.
A reader will be my pruchase today.