The obvious answer is that your computer needs more memory. Most likely 8GB of memory AND a 64-bit operating system will fix the problem. (Note: 8GB without a 64 bit operating system will not help)
In the meantime, you need to make sure there are no other programs open when you do the export (and if necessary shut down background processes like firewall and antivirus and anything else you can find), and export in small batches, or as single photos.
Thanks for the info
I had it repaired and LR worked great before the repair. I just checked computer info and it is set at 32 bits. I have 8gigs memory. From what l have read it's not a big deal switching back to 64 bit is. Thanks again. Keith