Hello, first time poster, long time reader... I have an 24" iMac alu (2.4 GHz, 320 GB HDD, 4 GB RAM) and I run OS X 10.5 Leopard. I installed WinXP SP2 using BootCamp. All worked out fine, until I upgraded my memory from 1 GB to 4 GB RAM. The RAM (Corsair, designed for mac) is fine, I did a hardware test just to rest assured theres nothing wrong with it. But, quelle surprise, WinXP didn't boot anymore. (XP should still boot with the additional RAM, however, it will only be able to use about 3.3 GB of it. Someone told me 32-bit Windows allocates some memory often what is above 3.2GB for PCI support. When it sees 4GB it probably wants to create a new pagefile too.) To boot in XP I have to press the "alt/option" key and I am able to select OS X or XP. If I double-click on the XP partition, the computer just freezes; nothing happens after that. The screen keeps displaying the two drives (XP and OS X) but the computer is frozen, the mouse cursor doesnt move, I have to shut it down. I've tried waiting for a couple of minutes, just to see if it's eventually booting in XP. It didn't, tho Whats weird: I can see the Win partition from OS X, I can browse the folders I cant access it tho (but its NTFS so thats understandable). This is what Ive tried and DIDNT work: (1) Safe Boot (Win): to do that, you have to press F8 while booting in XP. Doesn't work. To use this, Win has to start booting. Mine doesn't. (2) Boot from WinXP install CD: doesn't work. I power up the computer, keep pressing alt/option key and I'm able to choose to boot in OS X, in XP or from XP install CD. If I click on Macintosh HD for OS X, everything runs ok. If I click on Windows or XP install CD it freezes instantly. (3) Boot from Norton Ghost CD (I did a back-up image of the Win system back in the day when I installed it): doesn't work. Again, it freezes instantly. (4) Hold C during startup to force a boot of the CD (not holding alt/option): doesn't work... the screen just stays white (or grey, whatever). (5) Boot into OS X, leave the Windows CD in the drive, start BootCamp Assistant and select the 'Start the Windows Installer' option - the system should reboot onto the CD without any keyboard input (I was hoping to get into the Windows Install and take the 'Repair existing Windows' path): nothing. The screen just stays white. Basically, the moment I click on anything else than "Macintosh HD", it freezes INSTANTLY. I guess the only option is to delete that partition using BootCamp and try again So I deleted the Win partition (using BootCamp, of course) and made another one. When the time came to start the Win installer, I inserted the XP Install CD and waited. My mac restarted and then NOTHING. Again, a white screen. Please help, I ran out of ideas Thank you.