I know for sure the x64 version from ramdisk.tk works on Win7 x64. Never used the free version before, but it should support Win7 x64 with 1GB.
I've been using it since Win2003 days, best commercial RAMDisk software out there.
If you need don't feel like paying $12 for the full version w/o time limit, let me know through PM.
HTPC: E7300 | XFX GF9300 mATX | 2x2GB G.SKILL DDR2-1000 | Samsung F1 1TB | Slim BD-Combo ODD | HVR2200 & AverMedia TwinStar [4xDVB-T] | Windows7 x64 Ultimate
Server#1: Athlon II X4 630 | MSI 790FX-GD70 | Matrox 2D PCI | Samsung DDR3-1333 2x4GB ECC | Savvio 10K.2 146GB + DELL SAS 5/iR | 500GB 7200.11 | Dell PERC 5/E (+TBBU) | VMware ESXi 4.1
Server#2: Phenom II X4 945 | MSI 890FXA-GD70 | Matrox 2D PCI | Samsung DDR3-1333 2x4GB ECC | Savvio 10K.2 146GB + DELL SAS 5/iR | 500GB 7200.11 | Dell PERC 6/i + 8x1TB (+BBU) | Intel Pro/1000 PT Dual NIC | VMware ESXi 4.1