Re-allocating space on XP drive????

Hi guys

I have a question; I've just finished setting up my Vista - XP dual boot system (nearly killed me). When I used the Vista 'Shrink Drive' Tool so I could allocate some space and make a partition D drive, I stupidly only allocated 4 GB to the area on which I was going to install XP. Anyway Xp is all working, it's only as I've been installing all the drivers and apps that I notice the D drive with is the XP drive now only has 154mb of space left. I've read about re-allocating space from the vista end using the expand tool, can anyone tell me if that's going to be safe? I really don't want to upset my XP install as it's taken me ages to sort out. I just want to extend it's space a little. I could change a section of unused space to unallocated and then join it to the D drive (it's all NTFS). Is that going to work without hurting XP?

Any advice would be lovely......

thanks