Can a Canon S1 IS use a 4GB CF card.

I used a 512MB CF card and it works well. When I insert a 4GB CF card, the camera failed to recognise the card (the menu format item greyed out with no capacity shown) and I cannot format the card. The card works well in my Canon PowerShot A75 (shows 3.7GB). Please help.

I rather doubt it. 1GB is probably the max in that S1. You could check for a firmware update which opens it up, but even then, 2 GB is probably the ceiling.

BTW - I don't know if you're aware, but your camera was one of a host of cameras that suffered from a faulty CCD chip. Check out this from Canon regarding it.

Affected products:

- Digital Cameras A60, A70, A75, A300, A310, S230, SD100, SD110, A40(*), A80(*), A85(*), A95(*), S1 IS(*), S60(*), S200(*), S330(*), S400(*), S410(*), S500(*)

Malfunction:
It has been confirmed that the connecting parts of the internal wiring of the CCD used in affected products may become disconnected, especially if the affected products are stored or used in high-temperature and high-humidity environments. If this occurs, the signal is not output from the CCD normally in Shooting Mode, which may cause a distorted image or the absence of an image. This malfunction can be confirmed on the LCD monitor screen during shooting. The same malfunction also appears on the recorded image.

Canon's Response:
Effective immediately, and regardless of warranty status, Canon will repair, free of charge, the products listed above exhibiting the above-mentioned malfunction if Canon determines that the malfunction is caused by the CCD image sensor. Canon will also cover the cost of shipping and handling in connection with this repair.

So the good news is that Canon will fix it for FREE:

U.S. residents are kindly directed to contact the Canon Customer Support Center for further assistance at 1-800-828-4040. Support hours are Monday thru Friday - 8:00 AM to 12:00 midnight; and Saturday 10:00 AM to 8:00 PM (all times EST). Alternatively, if electronic support is preferred, please send your email to carecenter@cits.canon.com

Something to keep an eye on at least.