I don't think 7.4 is supported on W764-bit:
Windows OS Compatibility Alerts
Windows 7
The following versions of Pro Tools software are officially supported with Windows 7 Home Premium, Professional, or Ultimate (32 or 64-bit)
- Pro Tools 9.0, 9.0.1, 9.0.2, 9.0.3, and 9.0.5
- Pro Tools MP 9.0 and 9.0.5
- Pro Tools HD 8.5 (HD Native)
- Pro Tools LE 8.0.4 and 8.0.5
- Pro Tools M-Powered 8.0.4 and 8.0.5
Windows 7 Service Pack 1 is officially qualified with the following versions of Pro Tools.
(Not tested or qualified with other versions of Pro Tools)
- Pro Tools 9.0.2, 9.0.3, and 9.0.5
- Pro Tools MP 9.0 and 9.0.5
- Pro Tools LE 8.0.5
- Pro Tools M-Powered 8.0.5
- Pro Tools SE 8.0.3
- Pro Tools M-Powered Essential 8.0.3